Pscon01-02 (hpcl Nagaon).pdf

Electric Distribution System Study Report

Hindustan Paper Corporation Limited Nagaon Paper Mill

August 2001

Asea Brown Boveri Limited Maneja, Vadodara - 390 013 Tel : 0265 643259, Fax : 640718

Power System Studies : HPCL-Nagaon Paper Mill

Contents Page Executive Summary Chapter - I : Introduction 1.1 Why Power System Study 1.2 Applying Power System Analysis Techniques to Industrial Power

I-1 I-1

1.3 Power System Study for HPCL - Nagaon Paper Mill (HPCL-NPM) 1.3.1 About HPCL-NPM 1.3.2 Important Issues at HPCL-NPM 1.3.3 Studies proposed 1.3.4 Benefits of the Study

I-1 I-1 I-2 I-2 I-2

Systems

Chapter - II : System and Equipment Data 2.1 Introduction 2.2 Single Line Diagram 2.3 Captive Generation 2.4 State Grid 2.5 Operating Conditions 2.6 Equipment Data 2.6.1 Turbine Generators (TGs) 2.6.2 Cables and Overhead Line 2.6.3 Transformers 2.6.4 Loads 2.6.5 Protective Relays and Current Transformers 2.6.6 Miscellaneous Data 2.7 Measurements Carried Out 2.7.1 Load Measurements 2.7.2 Harmonic measurements 2.8 Data Mapping and Validation

II-1 II-1 II-1 II-1 II-1 II-4 II-4 II-5 II-6 II-7 II-7 II-7 II-7 II-7 II-10 II-11

Chapter - III : Load Flow Study and Analysis 3.1 Introduction to Load Flow Studies 3.2 Base Case Studies 3.2.1 Loading Conditions 3.2.2 Both TGs operating and Grid Isolated 3.2.3 One TG operating and Grid feeding considerable power 3.2.4 Both TGs out and Grid feeding power entirely 3.3 Reactive Power Compensation Studies 3.3.1 Cases with Load Power Factor :0.9 and 0.95 respectively 3.3.2 Lumped Reactive Power Requirement 3.3.3 Benefits of Reactive Power Compensation 3.4 Feeder Power Flow Optimization 3.4.1 Reduction in losses 3.5 Cost-Benefit Analysis of Improved Options 3.6 Motor Starting Studies 3.6.1 Significance of Motor Starting Studies 3.6.2 Study Cases and Results 3.7 Conclusion and Recommendations

III-1 III-1 III-1 III-1 III-2 III-2 III-3 III-3 III-4 III-6 III-6 III-7 III-8 III-10 III-10 III-10 III-14

Chapter - IV : Short Circuit Study 4.1 Introduction to short-Circuit Study

IV-1

Power System Studies : HPCL-Nagaon Paper Mill

4.2 Types of Short Circuit Faults 4.3 System and Equipment Data 4.4 Standard Followed 4.5 Short Circuit Studies 4.6 Reduction of Fault Current 4.7 Equipment Short Circuit Ratings 4.8 Conclusions and Recommendations

IV-1 IV-2 IV-4 IV-7 IV-10 IV-14 IV-14

Chapter - V : Relay Coordination Study 5.1 Introduction 5.2 Different Criteria Considered for Relay Coordination 5.3 Schemes used in Protection System 5.4 Relay Coordination for HPCL-NPM 5.4.1 Schemes and Relays present in HPCL-NPM 5.4.2 Nomenclature( for feeders upstream & downstream) 5.4.3 Co-ordination criteria for Study 5.4.4 Relay co-ordination for Different Condition of Operation 5.4.5 Summary of Relay Settings 5.4.6 Sample Calculations for DBB2 Feeder 5.5 State-of-the-art Protective relays 5.6 Conclusion and Recommendations

V-1 V-2 V-5 V-6 V-6 V-7 V-8 V-9 V-13 V-116 V-122 V-123

Chapter - VI : Transient Analysis 6.1 Introduction to Transient Analysis 6.2 Generator Control System Modeling 6.3 System Disturbances 6.3.1 Short-Circuits 6.3.2 Load Injection and Rejection 6.3.3 Loss of generation and load shedding 6.3.4 Loss of Grid supply 6.4 Conclusion

VI-1 VI-1 VI-2 VI-2 VI-4 VI-5 VI-6 VI-7

Chapter - VII: Harmonic Studies 7.1 Introduction to Power System Harmonics 7.2 Disadvantages of Power System Harmonics 7.2.1 Effects on Motors and Generators 7.2.2 Effects on Transformers 7.2.3 Effects on Power Cable 7.2.4 Effects on Capacitors 7.2.5 Effects on Switchgear and Relaying 7.3 Harmonic Measurements 7.4 Harmonic Analysis 7.4.1 Without Filters 7.4.2 Suppression of Harmonics 7.4.2.1 Harmonic Filter Bank 7.4.2.2 Analysis with Filter Bank 7.5 Conclusion and Recommendations

VII-1 VII-1 VII-1 VII-2 VII-2 VII-2 VII-2 VII-3 VII-3 VII-3 VII-5 VII-5 VII-6 VII-8

Chapter - VIII : Condition Monitoring and Diagnostics 8.1 Introduction to Condition Monitoring and Diagnostics(CMD) 8.2 Suggested CMD on Switchgear and Transformers 8.3 System Monitoring Sequence Event Recorder and Disturbance Recorder 8.4 Suggested Maintenance Practice 8.5 Recommendations

VIII-1 VIII-1 VIII-4 VIII-7 VIII-7

Power System Studies : HPCL-Nagaon Paper Mill

Chapter - IX : Conclusion and Recommendations

IX- 1- 4

Power System Studies : HPCL-Nagaon Paper Mill

Executive Summary The operation of an industrial power system requires comprehensive analysis to evaluate current system performance and to minimise system interruptions and their effect on overall operation of the plant. This also ascertains the effectiveness of alternative plans for system expansion. System study and analysis was carried out for HPCL-Nagaon Paper Mill (NPM) Power Supply System using computer software. Various studies like Load Flow (including Reactive Power Compensation and Motor Starting), Transient Stability, Short-Circuit, Relay Co-ordination and Harmonic Analysis were carried out. The total demand of NPM plant is 30.5MW which is entirely met with captive power generation having two 11kV, 15 MW TGs. The power system is also connected to Assam State Electricity Board (ASEB) grid via two 132/11 kV transformers of 7.5 MVA each. Normally, the plant runs on captive generation with ASEB grid isolated. Supply from ASEB grid is taken normally for some feeders as well as during emergency. Some of the critical issues addressed in system studies on the basis of feedback from NPM are: • Frequent unwanted tripping of TGs due to disturbances in downstream feeders • Low power factor at ASEB grid incomers attracting penalty charges. ABB engineers visited NPM for data collection, discussions with operating personnel to get details of problems faced and for measurement and validation of data. This data was mapped into CALPOS software for As-is Analysis, simulation and suggesting improvements. Following is the gist of system studies : Load Flow Studies •

Under normal operation with both TGs feeding the plant load entirely, the TGs are slightly overloaded (to105%) and all buses/elements are loaded within limits. Power factors at NB1 and NB2 buses feeding DC drives were found to be very poor.

•

When one TG is operating at rated condition and balance power is fed by the Grid, NPM has to pay penalty on account of low power factor (0.69 lagging). Further, both 7.5 MVA transformers are also overloaded.

•

The cables between ASEB buses and TG buses which are presently used only for charging ASEB buses for emergency load transfer can be loaded by closing bus couplers at ASEB buses, thereby reducing the losses and improving the voltage.

•

Major improvement options found were - Installation of 10.4 MVAR , 11kV shunt capacitors at three bus locations and 3 MVAR filter banks at two buses.

•

The above improvements call for an investment of Rs. 35-40 lakhs approximately on the Reactive Power Compensation and Filter Banks as mentioned above. This can result in annual savings to the tune of 25.9 lakhs plus the saving in low power factor penalty of 52.8 lakhs (as paid by HPCL-NPM in the year 2000-2001). This makes the payback of investment in approximately 6 months. Thereafter the net saving for the plant will be around 78.7 lakhs per annum. Additionally, the harmonics at Buses NB1 and NB2 will be suppressed resulting in better quality of power and prevention of bad effect of harmonics.

Power System Studies : HPCL-Nagaon Paper Mill •

Motor starting analysis with largest motor of 800kW was found to be in order in the sense that the bus voltage drop is less than 20%(allowable) even for two successive starting with time interval of 2.5 sec.

Short-Circuit Studies •

The short-circuit studies were carried out for the cases where both the Generators feeding power to the plant as well as only Grid feeding power to the plant. It is observed that the fault currents are of lower magnitudes.

Relay Co-ordination •

Relay co-ordination study was carried out for existing system and relay settings under various fault types and locations. It was found that relay settings need to be changed for proper coordination and to avoid nuisance tripping of TGs for any downstream fault. Recommended settings for existing relays are given in the detailed report.

•

For flexible and optimum relay co-ordination, it is recommended that numerical relays are used in place of existing electro-mechanical relays which are slow operating and have setting range limitations. The investment on numerical relays can very well be recovered from the reduced undesired trippings in the system which leads to loss of production, wastage of material under processing, additional energy drawn from ASEB grid at higher rates, TG start-up cost, etc.

Transient Stability •

Transient stability of system was carried out under different faults/disturbances with respect to existing as well as proposed relay settings. To avoid TG tripping on downstream fault, time delay relay have to be used with under-voltage relay.

•

The present settings of under-frequency relays are suitable to keep the system stable during injection or rejection of large load(s) in the system.

Harmonic Analysis •

Harmonics generated by DC drives on NB1 & NB2 buses can be reduced by installing filter banks of 1.5 MVAR capacity on each bus. This will also help in improving power factor from around 0.5 lag to above 0.9 lag.

Power System Studies : HPCL-Nagaon Paper Mill

Chapter - I

Introduction 1.1 Why Power System Study The planning, design and operation of industrial or commercial power systems require several studies to assist in the evaluation of the initial and future system performance, reliability, safety, and ability to grow with production or operating requirements. The studies most likely needed are load flow studies, short circuit studies, stability studies, and motor starting studies. These studies are required to help a plant engineer determine overall system needs before he proceeds with specific planning and engineering design. Additional studies of transients, reliability, grounding, and harmonics may also be required. The plant engineer in charge of system design must decide which studies are needed to ensure that the system will operate safely, economically, and efficiently over the expected life of the system. 1.2 Applying Power System Analysis Techniques to Industrial Power Systems As technology has advanced, so has the complexity of industrial and commercial power systems. These power systems have grown in recent decades with capacities far exceeding that of a small electric utility system. Today, plant management personnel are highly concerned with system interruptions and their effect on overall operation. Therefore, they demand assurances of maximum return on capital investment for any sizeable expansion. The complexity of modern industrial and commercial power systems has made manual performance of power system studies difficult and time consuming, if not impossible. However, through the use of digital computers these studies can be made with relative ease. Answers to many perplexing questions regarding impact of expansion on the system, short circuit capacity, stability, load distribution, etc, can be intelligently obtained. The recent advances in computer technology now enable engineers to simulate the system operation using computer software and change or modify the system to meet whatever design criteria may arise. 1.3 Power System Study for HPCL - Nagaon Paper Mill (HPCL-NPM) 1.3.1 About HPCL-NPM Hindustan Paper Corporation Limited (HPCL) is a Govt of India Enterprise under Department of Heavy Industry. It is one of the largest manufacturers of writing and printing paper in South East Asia. HPCL is the only paper manufacturer using Kamyr Continuous Digester for pulping of bamboo in India. The company has 5 production units and 3 subsidiaries with installed capacity of 351,000 MT. The Nagaon Paper Mill (NPM) situated at Jagi Road, district Marigaon, Assam is fifteen years old plant with installed capacity of 100,000MT of writing and printing paper and newsprint. NPM’s total average demand of 30.5MW is wholly met with captive power generation with two 11kV TGs of 15MW each at a power factor of 0.8 lagging. The electrical system is also connected to Assam State Electricity Board (ASEB) via two 132kV feeders which are stepped down to 11kV via two transformers of 7.5MVA each. There are total 46 numbers of transformers, which includes 8 numbers of 11/3.3 kV, 36 numbers of 11/0.415 kV and 2 numbers of 3-winding 10MVA and 0.8MVA transformers feeding to LT DC loads at C&C plant and CLO2 plant at 135 V and 41V respectively. There are two fault current limiting reactors connecting to Township and River intake pump transformer.

I-1

Power System Studies : HPCL-Nagaon Paper Mill As a standard practice, the plant runs on captive generation and ASEB grid is completely isolated. Supply from the ASEB grid is taken during emergency and sometimes some of the feeders are fed from grid but in isolation from the TG fed sub-system. This is to avoid any disturbance on grid to affect the captive generators. 1.3.2 Important Issues at HPCL-NPM • • • • • •

Frequent tripping of generator(s) due to disturbances in downstream feeders. Marginal overloading of generators due to normal plant demand of 30.5MW at 0.8 lag PF Operating frequency and voltage are kept below nominal values to reduce demand on generators. Harmonic distortion due to DC drives in the system. Low power factor at ASEB grid incomers attracting penalty charges. Flash-over in 11kV panels resulting in outage in power supply.

1.3.3 Studies proposed • • • • •

Load flow analysis Harmonic analysis Short circuit studies and Relay co-ordination Transient stability studies Motor starting analysis

1.3.4 Benefits of the Study The above mentioned studies have their individual advantages as described below : 1. Load flow studies: These studies are used to determine the best operating procedure for the system, especially in the event of a loss of one or more generating units and suddenly applied loads (impact loads). Load flow studies also determined the most suitable location of capacitors in the system for power factor improvement. This study offer valuable information regarding system losses, data for equipment specifications, overall system capability and limitations, proper settings of transformers in the system and optimisation of circuit usage in the system. This information decides the limitations on increasing load demands. 2. Harmonic studies: These studies are required to decide the harmonic level at Paper Mill which has DC drive used for paper cutting and packing. The study results provide the information about the generated harmonic effects on the system and decide the need of filtering those harmonics. 3. Short circuit studies and relay co-ordination: Whenever a fault occurs in an electrical power system, relatively high currents flow, producing large amounts of destructive energy in the form of heat and magnetic forces. A short circuit studies is performed to make sure that protective devices have adequate interrupting current capability and ensure power system components can withstand mechanical and thermal stresses that occur during a fault. It is also used to perform relay co-ordination which is the quality of selectivity among the protective devices during fault conditions. 4. Transient stability studies: These studies give the performance of the generators during transients on the system. These transients include a fault (any type), sudden load injection or rejection and sudden outage of one of the generator in the system. 5. Motor starting studies: These studies are required to know the starting effect of large synchronous or induction motors. It is preferable to start these motors across the line, if possible. This can cause severe voltage dips in the system however, and , in certain circumstances, the motor may not be able to break away from standstill or might stall during acceleration. These studies decides

I-2

Power System Studies : HPCL-Nagaon Paper Mill the need of starting device and their characteristics and starting span between two motors on the same bus.

Power System Studies : HPCL-Nagaon Paper Mill 2.2 Single Line Diagram of HPCL-NPM Network

II-2

Power System Studies : HPCL-Nagaon Paper Mill Single Line Diagram of HPCL-NPM Network - Feeders

II-3

Power System Studies : HPCL-Nagaon Paper Mill

Chapter - II

System and Equipment Data 2.1 Introduction The power system study requires various data like single line diagram, equipment data, operating conditions, average load on different feeders, cables, relays, etc. The validity of the solution depends on the accuracy of the data provided. Most of the data required for system study was provided by HPCL-NPM and some of the data was collected and measured by ABB engineers during their visits to the plant. Various data provided, collected and measured are tabulated here. 2.2 Single Line Diagram For any power system study single line representation of the network is the primary input required for understanding the system. The single line diagram for the Nagaon Paper Mill was made in CALPOS software as shown in figure 2.1. 2.3 Captive Generation The captive generation in the system has two Turbine Generators of 15 MW rating each which run in parallel but isolated from the grid. 2.4 State Grid The electrical system is connected to Assam State Electricity Board (ASEB) grid via two 132kV feeders. The voltage is stepped down to 11kV via two transformers of 7.5MVA each. 2.5 Operating Conditions Total connected load of the HPCL-NPM including township is about 30.5 MW with normal loading of about 22 MW. The power for the plant is entirely drawn from the captive power plant with two TGs of 15 MW each at 11kV. However sometimes for fulfilling minimum power consumption requirement from ASEB, some feeder is put on ASEB power from 132/11kV substation. Otherwise the entire plant runs in island mode. Supply is taken from ASEB grid during emergency conditions like fault or maintenance on captive generators. In order to keep the alternative supply ready for use, the grid transformers and ASEB buses at DBB1 and DBB2 are kept in charged condition. The operating conditions of the generators are as follows. Table 2.5(a): Normal operating conditions of Generators and Grid Power Supply GEN1 GEN2 ASEB

VL-L (rms) kV 10.87 10.87 11

Il (rms) kA 1.03 1.067 0.02

P Q (MW) (MVAR) 15.2 12.195 15.3 13 0.1 0.378

II-1

S (MVA) 19.5 20 0.391

P.F Frequency (lag) Hz 0.78 49.3 0.76 49.3 0.256 50

Power System Studies : HPCL-Nagaon Paper Mill

2.6 Equipment Data 2.6.1 Turbine Generators (TGs) Generator Name Rated Power Rated Active Power Rated Voltage Rated Current Rated Power Factor RPM Rated frequency X/R Ratio Generator Field Resistance at 20 °C Critical speed Inertia constant Maximum S.C. Torque Generator phase connection Insulation class Stator Rotor Steady d-axis reactance xd Transient d-axis reactance xd’ Sub-transient d-axis reactance xd’’ Negative sequence reactance X2 Zero sequence reactance X0 Open circuit d-axis transient time Tdo’ S.C. d-axis transient time Td”

TG1 18.75 MVA 15 MW 11 kV ± 5% 984 A 0.8 lag 3000 50 Hz ± 1% 0.6125 0.2676 Ohm 1700 rpm 0.495 Tm2 86500 kg.m Double Star

TG2 18.75 MVA 15 MW 11 kV ± 5% 984 A 0.8 lag 3000 50 Hz ± 1% 0.6125 0.2676 Ohm 1700 rpm 0.495 Tm2 86500 kg.m Double Star

B B 193 % 19.2 % 13.69 % 13.69 % 5.35 % 4.04 sec 0.403 sec

B B 193 % 19.2 % 13.69 % 13.69 % 5.35 % 4.04 sec 0.403 sec

S.C. d-axis sub-transient time Td” Armature S.C. time constant Ta Negative sequence current capacity

0.05 sec 0.1586 sec 8 % for continuous 13 % for 30 min. 13.15 x Ir(peak)

0.05 sec 0.1586 sec 8 % for continuous 13 % for 30 min. 13.15 x Ir(peak)

1.51 kA 2.408 kA

1.51 kA 2.408 kA

Maximum S.C. current (including DC component) Sustained 3-φ S.C. current Sustained 1-φ S.C. current

II-4

Power System Studies : HPCL-Nagaon Paper Mill

2.6.2 Cables and Overhead Line Table 2.6(a): Cable Data

XLPE XLPE XLPE XLPE

No. of Runs 3 1 3 3

Cable No. of Cores 3 3 3 3

75

XLPE

1

3

300

DBB-1

1100

XLPE

3

3

300

NB1 Utmal M/C NC1 Utmal M/C ND1 Utmal M/C NG Power House NI/NM Water Treat

250 250 300 30

XLPE XLPE XLPE XLPE

2 2 2 2

3 3 3 3

300 300 300 300

700

XLPE

1

3

300

11 kV Bus B 11 kV Bus B 11 kV Bus B 11 kV Bus B 11 kV Bus B

NH Power House NE Bleach Plant NI/NE Water Treat NC2 Jessop M/C DBB-1

30 300 700 300 10

XLPE XLPE XLPE XLPE XLPE

2 1 1 1 3

3 3 3 3 3

300 300 300 300 300

17 18 19 20

DBB-1 DBB-1 DBB-1 DBB-1

NL Chipper NF Digester NB2 Jessop M/C ND2 Jessop M/C

600 300 350 350

XLPE XLPE XLPE XLPE

1 1 2 2

3 3 3 3

300 300 300 300

21

DBB-1

NA River Intake

900

XLPE

1

3

300

22

ND1 (11kV) T3 Secondary NI (11kV) T3 Secondary NG (11kV) T3 Secondary NH (11kV) T3 Secondary NC2 (11kV) T3 Secondary ND2 (11kV) T3 Secondary NL (11kV) T3 Secondary NF (11kV) T3 Secondary

T3 Primary 3.3 kV Bus T3 Primary 3.3 kV Bus T3 Primary 3.3 kV Bus T3 Primary 3.3 kV Bus T3 Primary 3.3 kV Bus T3 Primary 3.3 kV Bus T3 Primary 3.3 kV Bus T3 Primary 3.3 kV Bus

50 70 15 25 90 110 70 90 50 70 40 60 15 45 30 45

XLPE XLPE XLPE XLPE XLPE XLPE XLPE XLPE XLPE XLPE XLPE XLPE XLPE XLPE XLPE XLPE

1 4 1 4 1 4 1 4 1 4 1 4 1 4 1 4

3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3

300 300 300 300 300 300 300 300 300 300 300 300 300 300 300 300

Sr. No

From Bus (11kV)

To Bus (11kV panel)

1 2 3 4

DBB-2 DBB-2 DBB-2 DBB-2

NK C&C NJ Lagoon 11 kV Bus C (S/S) 11 kV Bus A (P/H)

5

11 kV Bus C

NN Township

6

11 kV Bus C

7 8 9 10

11 kV Bus A 11 kV Bus A 11 kV Bus A 11 kV Bus A

11

11 kV Bus A

12 13 14 15 16

23 24 25 26 27 28 29

Overhead Line Data

Cable Length (m) 400 250 10 1100

Cable Type

Size

Remark

(mm2)

300 300 300 300 Up to O/H Line

Up to O/H line

Power System Studies : HPCL-Nagaon Paper Mill From : DBB1 (from Cable-end) Conductor Type : Wolf 2.6.3 Transformers Transformer Name LAGO_XFR TR_1 TR_2 TR_LCC5 TR_NB11 TR_NB12 TR_NB13 TR_NB21 TR_NB22 TR_NB23 TR_NC11 TR_NC12 TR_NC13 TR_NC21 TR_NC22 TR_NC23 TR_ND11 TR_ND12 TR_ND13 TR_ND21 TR_ND22 TR_ND23 TR_NE1 TR_NE2 TR_NE3 TR_NF1 TR_NF2 TR_NF3 TR_NG1 TR_NG2 TR_NH1 TR_NH2 TR_NH3 TR_NH4 TR_NI1 TR_NI2 TR_NL1 TR_NL2 TR_NL3 TR_NN1 TR_NN2 TR_NN3 TR_NN4 TR_NN5 TR_RIVER

Vector Group Dyn11 YNyn0 YNyn0 Dyn11 Dyn11 Dyn11 Dyn11 Dyn11 Dyn11 Dyn11 Dyn11 YNyn0 Dyn11 Dyn11 Dyn11 YNyn0 YNyn0 Dyn11 Dyn11 YNyn0 Dyn11 Dyn11 Dyn11 Dyn11 Dyn11 YNyn0 Dyn11 Dyn11 Dyn11 YNyn0 Dyn11 YNyn0 Dyn11 Dyn11 YNyn0 Dyn11 YNyn0 Dyn11 Dyn11 Dyn11 Dyn11 Dyn11 Dyn11 Dyn11 YNyn0

To : Hathyamukh Length of Line : 6.2 kms

II-5 Primary Secondary Impedance (kV) (kV) Z (%) 11 0.415 5.6 132 11 7.5 132 11 7.5 11 0.415 4.52 11 0.415 5.6 11 0.415 5.6 11 0.415 5.6 11 0.415 5.6 11 0.415 5.6 11 0.415 5.6 11 0.415 4.52 11 3.3 4.65 11 0.415 5.6 11 0.415 4.52 11 0.415 5.6 11 3.3 4.65 11 3.3 4.65 11 0.415 5.6 11 0.415 5.6 11 3.3 4.65 11 0.415 5.6 11 0.415 5.6 11 0.415 5.6 11 0.415 5.6 11 0.415 4.52 11 3.3 4.65 11 0.415 5.6 11 0.415 5.6 11 0.415 5.6 11 3.3 4.65 11 0.415 5.6 11 3.3 5.68 11 0.415 5.6 11 0.415 4.52 11 3.3 4.65 11 0.415 5.6 11 3.3 4.65 11 0.415 5.6 11 0.415 4.52 11 0.415 5 11 0.415 5 11 0.415 4.52 11 0.415 4.52 11 0.415 4.52 11 3.3 4.65

II-6

Power (MVA) 1.6 7.5 7.5 0.25 1.6 1.6 1.6 1.6 1.6 1.6 0.25 3 1.6 0.25 1.6 3 3 1.6 1.6 3 1.6 1.6 1.6 1.6 0.25 3 1.6 1.6 1.6 3 1.6 5 1.6 0.25 3 1.6 3 1.6 0.25 0.5 0.5 0.25 0.25 0.25 3

Power System Studies : HPCL-Nagaon Paper Mill

TR_SS14 CLO2_XFR RECT_XFR 2.6.4 Loads

Dyn11 Dyn11yn11 Dyn11yn11

11 11 11

0.415 0.041 0.135

5.6 9 11.38

1.6 0.8 10

Table 2.6(c) : Average Load in Different Feeders

Feeder Name

Ave. Real Power (MW)

NK C&C Plant NJ Lagoon NN Township NB1 Utmal M/C NC1/ND1 Utmal M/C NG/NH Power House NE Bleach Plant NI/NM Water Treat NC2/ND2 Jessop M/C NL Chipper NF Digester NB2 Jessop NA River Intake Total (Average)

7 0.4 0.6 1 4.7 5.3 2.1 1.1 3.9 0.7 2.2 1.1 0.4 30.5

Power Factor (lagging) 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8

2.6.5 Protective Relays and Current Transformers The details of protection schemes, associated relays and current transformer ratios which are important for relay co-ordination studies are listed in chapter - V (Relay Co-ordination). 2.6.6 Miscellaneous Data The operating configuration i.e. either normally open or normally closed status of the bus couplers and the alternate feeding elements were obtained. In addition, details of current limiting rectors and capacitor banks wherever existing were collected. 2.7 Measurements Carried Out ABB engineers visited the HPCL-NPM plant to collect/validate data for system studies, particularly the present relay settings, relay characteristics and available setting ranges at various relays and to measure the operating load and harmonics injections at different nodes. These measurements were done by using a Clamp-on Power Meter, Type-CW140 Yokogawa Japan make. It does the measurement of current, voltage, unbalance in voltage, power, power factor and energy. It also measures harmonic in currents and voltages and Total Harmonic Distortion (THD). 2.7.1 Load Measurements Most of the operating loads at 3.3 kV and 415V are measured and are tabulated as under :

II-7

Power System Studies : HPCL-Nagaon Paper Mill

Table 2.7 (a) : Operating Voltage and Current Measurements

USS12

VR (kV) 0.246

VY (kV) 0.229

VB (kV) 0.221

IR (kA) 1.15

IY (kA) 1.15

IB (kA) 1.18

USS11 MCC6 MCC7 USS15 MCC8 USS16 LCC4 USS14 C&CRECT MCC5 LCC3 MCC10 USS13 CLO2PL USS7 USS10 USS9 MCC2 MCC1 MCC3 MCC4 NB22 NB21 NB11 NB12 NB13 NB23 USS2 USS3 USS1 USS4 USS6 USS5 TWN25 TWN5 LAGOON GEN1 GEN2 NC11KV

0.2341 1.774 1.908 0.244 1.9 0.24 0.23 0.2294 6.27 1.9 0.23 1.9 0.242 6.293 0.241 0.241 0.24 1.881 1.9 1.9 1.9 0.24 0.242 0.24 0.2338 0.245 0.24 0.231 0.231 0.231 0.254 0.225 0.242 0.231 0.231 0.243 6.247 6.261 6.189

0.2339 1.774 1.907 0.244 1.9 0.239 0.23 0.2288 6.28 1.9 0.23 1.9 0.242 6.293 0.236 0.24 0.24 1.881 1.9 1.9 1.9 0.239 0.242 0.24 0.2338 0.245 0.24 0.231 0.231 0.231 0.254 0.225 0.243 0.231 0.231 0.243 6.261 6.26 0.6374

0.2342 1.75 1.899 0.243 1.9 0.239 0.23 0.2184 6.28 1.9 0.23 1.9 0.242 6.293 0.24 0.24 0.24 1.859 1.9 1.9 1.9 0.238 0.24 0.238 0.2338 0.244 0.24 0.231 0.231 0.231 0.254 0.225 0.243 0.231 0.231 0.243 6.241 6.228 0.6262

1.13 0.55 0.32 0.59 0.09 1.39 0.151 1 0.334 0.15 0.075 0.07 0.69 0.434 1.04 1.2 0.9 0.34 0.345 0.23 0.3 1.16 0.77 1.22 0.75 0.82 0.82 1.34 1.27 1.175 0.9 0.95 0.64 0.09 0.35 0.5 0.892 0.897 0.3

1.11 0.56 0.31 0.58 0.09 1.43 0.151 1.02 0.335 0.15 0.075 0.07 0.7 0.434 1.01 1.21 0.9 0.31 0.345 0.23 0.3 1.17 0.74 1.15 0.75 0.92 0.82 1.34 1.27 1.175 0.9 0.95 0.62 0.09 0.35 0.51 0.895 0.894 0.299

1.13 0.54 0.31 0.61 0.09 1.42 0.151 1.01 0.335 0.15 0.075 0.07 0.7 0.434 1.01 1.2 0.9 0.32 0.345 0.23 0.3 1.17 0.72 1.15 0.75 0.83 0.82 1.34 1.27 1.175 0.9 0.95 0.62 0.09 0.35 0.5 0.9 0.902 0.299

Location

Power System Studies : HPCL-Nagaon Paper Mill

Table 2.7 (b) : Power Measurements II-8 I-7 Location USS12 USS11 MCC6 MCC7 USS15 MCC8 USS16 LCC4 USS14 C&CRECT MCC5 LCC3 MCC10 USS13 CLO2PL USS7 USS10 USS9 MCC2 MCC1 MCC3 MCC4 NB22 NB21 NB11 NB12 NB13 NB23 USS2 USS3 USS1 USS4 USS6 USS5 TWN25 TWN5 LAGOON GEN1 GEN2 NC11KV

P Q (MW) (MVAR) 0.67 0.45 0.6 0.51 2.6 1.4 1.4 1.13 0.37 0.41 0.77 0.086 0.56 5 0.684 0.044 0.319 0.4558 0.63 0.61 0.7 0.52 1.44 1.573 1.049 1.368 0.37 0.25 0.42 0.247 0.25 0.25 0.752 0.713 0.6595 0.576 0.513 0.38 0.051 0.0671 0.31 13.3 13 4.845

0.23 0.308 0.66 0.588 0.38 3.8 0.513 0.0272 0.2397 0.2653 0.4725 0.38 0.52 0.3866 1.08 1.179 0.7847 1.026 0.75 0.47 0.72 0.46 0.56 0.56 0.545 0.516 0.477 0.372 384 0.26 0.03595 0.045 0.19 10 10 2.845

S (MVA) 0.81 0.79 2.9 1.8

PF (lag) 0.83 0.763 0.87 0.809

PA (deg)_ 33.9 40.2 29.5 36

Freq. (Hz) 49.16 49.16 49.16 49.1

U.R. % 6.5 0.1 0.3 0.3

0.43 0.513 1.02 0.104 0.69 6.3 0.855 0.0517 0.399 0.53 0.7875 0.73 0.87 0.648 1.8 1.966 1.31 1.71 0.83 0.54 0.84 0.526 0.6 0.6 0.9286 0.88 0.814 0.6858 0.641 0.45 0.0624 0.0808 0.37 17 17 5.645

0.846 0.8 0.757 0.825 0.829 0.798 0.8 0.85 0.8 0.86 0.8 0.839 0.803 0.803 0.8 0.8 0.8 0.8 0.449 0.466 0.509 0.47 0.496 0.496 0.81 0.81 0.81 0.84 0.8 0.824 0.83 0.83 0.85 0.8 0.8 0.9

32.2 36.87 40.9 34.4 34 37.2 36.87 31.8 36.87 30.86 36.87 32.9 36.6 36.58 36.87 36.87 36.87 36.87 63.8 62.2 59.4 61.96 60.2 60.2 35.9 35.9 35.9 32.86 36.87 34.4 33.9 33.9 31.9 36.89 38.1 30.4

49.2 49.2 49.17 49.2 49.11 49.2 49.2 49.2 49.2 49.06 49.2 49.1 49.18 49.2 49.05 49.2 49.2 49.2 49.22 49.16 49.15 49.2 49.24 49.2 49.2 49.2 49.2 49.2 49.2 49.16 49.2 49.2 49.32 49.3 49.3 49.1

0.2 0 0.3 0 2.9 0.2 0 0 0 0.1 0 1.2 0.3 0 0.8 0 0 0 0.5 0.5 0.6 0 0.5 0.5 0 0 0 0 0 0.3 0 0 0.2 0 0 0

Power System Studies : HPCL-Nagaon Paper Mill

2.7.2 Harmonic measurements

II-9 The following table gives the harmonic levels at various points for operating conditions. Locations Harmonic NB11 & NB12 & (Order) NB22 NB21 Voltage Harmonic Magnitude (%) V1CONT(1) 100 100 V1CONT(2) 0.22 0.3 V1CONT(3) 0.16 0.9 V1CONT(4) 0.18 0.4 V1CONT(5) 6.54 6 V1CONT(6) 0.06 0.8 V1CONT(7) 2.98 3.9 V1CONT(8) 0.22 0.7 V1CONT(9) 0.22 0.3 V1CONT(10) 0.22 0.7 V1CONT(11) 2.82 2 V1CONT(12) 0.22 0.2 V1CONT(13) 0.76 0.9 Voltage Harmonic Phase Angle V1PA(1) -62.06 -55.9 V1PA(2) -86.92 -64.6 V1PA(3) -125.7 -174.6 V1PA(4) 51.97 45.9 V1PA(5) 130.54 145.3 V1PA(6) 112.8 -9.9 V1PA(7) -176.94 -171.9 V1PA(8) -115.94 -12.4 V1PA(9) -7.54 -123 V1PA(10) 65.88 -25.4 V1PA(11) -77.38 -71.8 V1PA(12) -161.43 37.4 V1PA(13) -26.18 -20.8 Total Harmonic Distortion in Voltage (%) THD(IEEE)_V1 7.78 7.7 THD(IEEE)_V2 8.52 7 THD(IEEE)_V3 8.5 8.6 Current Harmonic Magnitude (%) I1CONT(1) 100 100 I1CONT(2) 1.9 15.5 I1CONT(3) 1.48 1.7 I1CONT(4) 1.72 10.3 I1CONT(5) 39.22 46.1

NB13 & NB23

NB1& NB2 Pri

100 0.2 0.44 0.36 1.3 0.32 0.82 0.42 0.2 0.28 0.74 0.18 0.26

100 0.2 0.4 0.3 1.4 0.2 0.7 0.3 0.3 0.2 0.8 0.2 0.4

-50.7 -19.88 -57.57 -167.07 139.4 -56.7 34.26 -125.48 24.42 126.5 -101.2 -35.4 -94.45

-150.6 -23.4 76.9 87.9 158.8 -16.3 -37.3 -57.4 -39.8 -16.4 -116.3 -57.7 -85.2

2.04 2.98 2.24

2 337.9 1.9

100 5 2 3.48 7.98

100 12.9 8.9 7.3 39.6

Power System Studies : HPCL-Nagaon Paper Mill

I1CONT(6) I1CONT(7) I1CONT(8) I1CONT(9) I1CONT(10) I1CONT(11) I1CONT(12) I1CONT(13)

0.36 9.88 0.46 0.64 0.7 6.78 0.54 2.12

3.2 1.05 16 3.43 2.1 0.73 1.3 0.88 2.7 1.35 6.4 2.05 1.1 0.65 4.3 1.03 Locations II-10 NB12 & NB13 & NB21 NB23

NB1& NB2 Pri

57.93 -85.13 70.58 -15.2 -36.08 40.55 -101.08 -49.83 -102.77 76.75 -5.93 -9.8 -2.58

150.6 -118.5 169.1 117.1 -6.6 -101.2 151.8 -60.5 38.6 -41.5 -14.8 -98.5 126.4

12.38 12.58 12.88

45 488.7 45.4

Harmonic NB11 & (Order) NB22 Current Harmonic Phase Angle I1PA(1) 62.06 55.9 I1PA(2) -14.06 50 I1PA(3) 118.26 58.1 I1PA(4) 36.08 118.7 I1PA(5) 170.08 147.1 I1PA(6) -85.58 -55.7 I1PA(7) -10.46 -47.4 I1PA(8) 8.18 36.2 I1PA(9) -78.7 -132.1 I1PA(10) 139.94 -114.7 I1PA(11) -20.56 -73.2 I1PA(12) -5.82 65.8 I1PA(13) 32.46 87.1 Total Harmonic Distortion in Current (%) THD(IEEE)_I1 41.24 53.1 THD(IEEE)_I2 39.92 53.5 THD(IEEE)_I3 39.56 53.7

3.3 8.7 1 1.3 1 7.4 1.1 1.4

2.8 Data Mapping and Validation The data thus obtained was mapped into the Power System Analysis Software (CALPOS) developed by ABB. Initially the as-is study was carried out to validate the data as well as the simulation approach. Most of the conditions actually occurring in the field could be simulated successfully.

Table 3.5 : Summary of Various Improvement Options Condition

Base Case

With Parallel Feeding

With Parallel Feeding and Reactive Power Compensation Reactive Power Compensation Without Parallel Feeding Reactive Power Compensation With One Generator Out Reactive Power Compensation With Both The Generators Out

Load Factor

1.0

1.0

1.0

1.0

0.8

0.45

TG1

TG2

ASEB

Losses

Reactive Power (MVAR)

12.5

Power (MW)

15.2

15.754

0.1

2.462

Reactive Power (MVAR)

12.5

13.11

0

3.182

Power (MW)

15.2

15.671

0

2.279

Reactive Power (MVAR)

6.2

6.251

0

3.170

Power (MW)

15.2

15.608

0

2.153

Reactive Power (MVAR)

6.3

6.347

-0.022

3.211

Power (MW)

15.2

15.632

0.100

2.277

Reactive Power (MVAR)

OFF

5.451

2.645

3.252

Power (MW)

OFF

14.573

10.265

1.904

Reactive Power (MVAR)

OFF

OFF

0.228

3.205

Power (MW)

OFF

12.788

OFF

III-9

0.378

14.707

Voltages at important buses DBB1

DBB2

NK

3.229

1.782

Voltage (%)

99.98

96.97

96.02

Voltage (%)

99.97

98.47

97.53

Voltage (%)

99.97

98.56

97.67

Voltage (%)

99.99

97.15

96.25

Voltage (%)

96.55

97.89

97.18

Voltage (%)

96.89

98.76

98.40

Power System Studies : HPCL-Nagaon Paper Mill

Short Circuit Study Results Table 4.1 : Both Generators and Grid feeding power to the plant Three-Phase & LG, LL, LLG Faults: Bus Information =================== ID kV ------------ -----A+B 11.00 ASEB 132.00 BUS C 11.00 DBB1 11.00 DBB2 11.00 LAGOON 0.41 NA 11.00 NA1 11.00 NB1 11.00 NB2 11.00 NB11 0.41 NB12 0.41 NB13 0.41 NB21 0.41 NB22 0.41 NB23 0.41 NC1 11.00 NC2 11.00 NC11 0.41 NC12 3.30 NC13 0.41 NC21 0.41 NC22 3.30 NC23 0.41 NC_22P 11.00 NC_22S 3.30 ND1 11.00 ND2 11.00 ND11 3.30 ND11_S 3.30 ND12 0.41 ND13 0.41 ND21 3.30 ND21_P 11.00 ND21_S 3.30 ND22 0.41 ND23 0.41 ND_11P 11.00 NE 11.00 NE1 0.41 NE2 0.41 NE3 0.41 NE4_1 0.11 NE4_2 0.11 NF 11.00 NF1 3.30 NF1_P 11.00 NF1_S 3.30 NF2 0.41 NF3 0.41 NG 11.00 NG1 3.30 NG1_P 11.00 NG1_S 3.30 NG2 0.41 NH 11.00 NH1 3.30 NH1_P 11.00 NH1_S 3.30 NH2 0.41 NH3 0.41 NH4 0.41 NI 11.00 NI1 3.30 NI1_P 11.00 NI1_S 3.30 NI2 0.41 NJ 11.00 NK 11.00 NK1_1 0.14 NK1_2 0.14 NK2 0.41 NK3 0.41 NL 11.00 NL1 3.30 NL1_P 11.00 NL1_S 3.30 NL2 0.41 NL3 0.41 NM 11.00 RIVER_WAT 3.30 TOWNSHIP 11.00

( Prefault Voltage = Bus Nominal Voltage )

3-Phase Fault ==================== I"k ip Ik ------ ------ -----10.16 18.97 10.16 31.50 77.77 31.50 11.20 28.71 11.20 10.16 18.97 10.16 11.19 28.46 11.19 35.88 79.85 35.88 4.78 6.93 4.78 3.42 4.99 3.42 9.18 15.32 9.18 8.78 14.22 8.78 35.75 78.51 35.75 35.75 78.51 35.75 35.75 78.51 35.75 35.64 77.35 35.64 35.64 77.35 35.64 35.64 77.35 35.64 9.18 15.32 9.18 7.83 12.06 7.83 7.82 17.09 7.82 9.02 19.36 9.02 35.75 78.51 35.75 7.80 16.90 7.80 8.43 15.60 8.43 35.33 74.57 35.33 7.48 11.37 7.48 8.72 17.15 8.72 8.98 14.75 8.98 8.98 14.75 8.98 8.66 16.77 8.66 8.93 18.57 8.93 35.69 77.92 35.69 35.69 77.92 35.69 8.71 17.10 8.71 8.66 13.92 8.66 8.94 18.67 8.94 35.69 77.92 35.69 35.69 77.92 35.69 8.58 13.73 8.58 7.83 12.06 7.83 35.33 74.57 35.33 7.80 16.90 7.80 7.80 16.90 7.80 455.22 774.95 455.22 455.22 774.95 455.22 7.83 12.06 7.83 8.57 16.28 8.57 7.62 11.63 7.62 8.75 17.33 8.75 35.33 74.57 35.33 35.33 74.57 35.33 10.05 18.45 10.05 8.63 16.64 8.63 9.34 15.81 9.34 9.04 19.58 9.04 36.00 81.18 36.00 10.05 18.45 10.05 8.74 17.29 8.74 9.50 16.33 9.50 9.07 19.81 9.07 36.00 81.18 36.00 7.84 17.22 7.84 36.00 81.18 36.00 5.55 8.09 5.55 8.04 14.02 8.04 5.48 7.99 5.48 8.15 14.44 8.15 34.22 66.81 34.22 9.63 16.76 9.63 10.50 20.84 10.50 267.48 618.03 267.48 267.48 618.03 267.48 36.13 82.77 36.13 7.84 17.29 7.84 6.01 8.82 6.01 7.94 13.67 7.94 5.77 8.44 5.77 8.26 14.86 8.26 34.51 68.60 34.51 7.77 16.58 7.77 5.55 8.09 5.55 4.57 8.10 4.57 10.86 23.66 10.86

Line-to-Ground Fault =========================== I"k ip Ib Ik ------ ------ ------ -----9.23 17.23 9.23 9.23 31.50 77.77 31.50 31.50 11.20 28.71 11.20 11.20 9.23 17.23 9.23 9.23 11.19 28.44 11.19 11.19 37.65 83.79 37.65 37.65 3.14 4.55 3.14 3.14 2.23 3.25 2.23 2.23 7.64 12.75 7.64 7.64 7.08 11.47 7.08 7.08 37.56 82.48 37.56 37.56 37.56 82.48 37.56 37.56 37.56 82.48 37.56 37.56 37.48 81.35 37.48 37.48 37.48 81.35 37.48 37.48 37.48 81.35 37.48 37.48 7.64 12.75 7.64 7.64 5.92 9.12 5.92 5.92 7.91 17.28 7.91 7.91 9.94 21.34 9.94 9.94 37.56 82.48 37.56 37.56 7.89 17.09 7.89 7.89 9.18 16.98 9.18 9.18 37.27 78.67 37.27 37.27 5.54 8.42 5.54 5.54 9.73 19.13 9.73 9.73 7.36 12.08 7.36 7.36 7.36 12.08 7.36 7.36 9.36 18.14 9.36 9.36 9.87 20.54 9.87 9.87 37.52 81.91 37.52 37.52 37.52 81.91 37.52 37.52 9.45 18.55 9.45 9.45 6.93 11.13 6.93 6.93 9.88 20.64 9.88 9.88 37.52 81.91 37.52 37.52 37.52 81.91 37.52 37.52 6.83 10.92 6.83 6.83 5.92 9.12 5.92 5.92 37.27 78.67 37.27 37.27 7.89 17.09 7.89 7.89 7.89 17.09 7.89 7.89 566.98 965.20 566.98 566.98 566.98 965.20 566.98 566.98 5.92 9.12 5.92 5.92 9.41 17.88 9.41 9.41 5.69 8.69 5.69 5.69 9.75 19.31 9.75 9.75 37.27 78.67 37.27 37.27 37.27 78.67 37.27 37.27 9.03 16.57 9.03 9.03 9.14 17.62 9.14 9.14 7.88 13.33 7.88 7.88 9.96 21.56 9.96 9.96 37.73 85.09 37.73 37.73 9.03 16.57 9.03 9.03 9.34 18.46 9.34 9.34 8.12 13.96 8.12 8.12 9.97 21.79 9.97 9.97 37.73 85.09 37.73 37.73 7.92 17.39 7.92 7.92 37.73 85.09 37.73 37.73 3.74 5.46 3.74 3.74 9.10 15.87 9.10 9.10 3.69 5.38 3.69 3.69 9.32 16.50 9.32 9.32 36.53 71.31 36.53 36.53 8.32 14.49 8.32 8.32 9.86 19.56 9.86 9.86 299.80 692.71 299.80 299.80 299.80 692.71 299.80 299.80 37.82 86.66 37.82 37.82 7.92 17.46 7.92 7.92 4.14 6.07 4.14 4.14 8.79 15.13 8.79 8.79 3.93 5.75 3.93 3.93 9.39 16.90 9.39 9.39 36.73 73.00 36.73 36.73 7.87 16.79 7.87 7.87 3.74 5.46 3.74 3.74 5.14 9.11 5.14 5.14 10.56 23.01 10.56 10.56

Line-to-Line Fault =========================== I"k ip Ib Ik ------ ------ ------ -----8.80 16.43 8.80 8.80 27.28 67.35 27.28 27.28 9.70 24.86 9.70 9.70 8.80 16.43 8.80 8.80 9.69 24.64 9.69 9.69 31.07 69.15 31.07 31.07 4.14 6.00 4.14 4.14 2.97 4.32 2.97 2.97 7.95 13.27 7.95 7.95 7.60 12.31 7.60 7.60 30.96 67.99 30.96 30.96 30.96 67.99 30.96 30.96 30.96 67.99 30.96 30.96 30.86 66.98 30.86 30.86 30.86 66.98 30.86 30.86 30.86 66.98 30.86 30.86 7.95 13.27 7.95 7.95 6.78 10.44 6.78 6.78 6.78 14.80 6.78 6.78 7.81 16.77 7.81 7.81 30.96 67.99 30.96 30.96 6.76 14.63 6.76 6.76 7.30 13.51 7.30 7.30 30.60 64.58 30.60 30.60 6.48 9.84 6.48 6.48 7.55 14.86 7.55 7.55 7.78 12.77 7.78 7.78 7.78 12.77 7.78 7.78 7.50 14.53 7.50 7.50 7.73 16.08 7.73 7.73 30.91 67.48 30.91 30.91 30.91 67.48 30.91 30.91 7.54 14.81 7.54 7.54 7.50 12.06 7.50 7.50 7.74 16.17 7.74 7.74 30.91 67.48 30.91 30.91 30.91 67.48 30.91 30.91 7.43 11.89 7.43 7.43 6.78 10.44 6.78 6.78 30.60 64.58 30.60 30.60 6.76 14.63 6.76 6.76 6.76 14.63 6.76 6.76 394.23 671.13 394.23 394.23 394.23 671.13 394.23 394.23 6.78 10.44 6.78 6.78 7.42 14.10 7.42 7.42 6.60 10.08 6.60 6.60 7.58 15.01 7.58 7.58 30.60 64.58 30.60 30.60 30.60 64.58 30.60 30.60 8.70 15.97 8.70 8.70 7.48 14.41 7.48 7.48 8.09 13.69 8.09 8.09 7.83 16.96 7.83 7.83 31.17 70.31 31.17 31.17 8.70 15.97 8.70 8.70 7.57 14.97 7.57 7.57 8.23 14.14 8.23 8.23 7.85 17.15 7.85 7.85 31.17 70.31 31.17 31.17 6.79 14.91 6.79 6.79 31.17 70.31 31.17 31.17 4.80 7.01 4.80 4.80 6.96 12.14 6.96 6.96 4.75 6.92 4.75 4.75 7.06 12.51 7.06 7.06 29.64 57.86 29.64 29.64 8.34 14.52 8.34 8.34 9.09 18.05 9.09 9.09 231.64 535.23 231.64 231.64 231.64 535.23 231.64 231.64 31.29 71.68 31.29 31.29 6.79 14.97 6.79 6.79 5.21 7.64 5.21 5.21 6.88 11.84 6.88 6.88 5.00 7.31 5.00 5.00 7.15 12.87 7.15 7.15 29.89 59.41 29.89 29.89 6.73 14.35 6.73 6.73 4.80 7.01 4.80 4.80 3.96 7.01 3.96 3.96 9.41 20.49 9.41 9.41

All fault currents are in rms kA. Current ip is calculated using Method C. * LLG fault current is the larger of the two faulted line currents.

Line-to-Line-to-Grd* =========================== I"k ip Ib Ik ------ ------ ------ -----10.79 20.13 10.79 10.79 31.50 77.77 31.50 31.50 11.20 28.71 11.20 11.20 10.79 20.13 10.79 10.79 11.23 28.55 11.23 11.23 37.35 83.11 37.35 37.35 4.56 6.60 4.56 4.56 3.20 4.65 3.20 3.20 9.54 15.92 9.54 9.54 9.04 14.64 9.04 9.04 37.37 82.06 37.37 37.37 37.37 82.06 37.37 37.37 37.37 82.06 37.37 37.37 37.38 81.14 37.38 37.38 37.38 81.14 37.38 37.38 37.38 81.14 37.38 37.38 9.54 15.92 9.54 9.54 7.89 12.15 7.89 7.89 7.89 17.24 7.89 7.89 9.91 21.26 9.91 9.91 37.37 82.06 37.37 37.37 7.89 17.10 7.89 7.89 8.93 16.52 8.93 8.93 37.40 78.95 37.40 37.40 7.48 11.37 7.48 7.48 9.88 19.43 9.88 9.88 9.29 15.26 9.29 9.29 9.29 15.26 9.29 9.29 9.27 17.96 9.27 9.27 9.91 20.61 9.91 9.91 37.38 81.60 37.38 37.38 37.38 81.60 37.38 37.38 9.28 18.22 9.28 9.28 8.89 14.29 8.89 8.89 9.91 20.69 9.91 9.91 37.38 81.60 37.38 37.38 37.38 81.60 37.38 37.38 8.80 14.07 8.80 8.80 7.89 12.15 7.89 7.89 37.40 78.95 37.40 37.40 7.89 17.10 7.89 7.89 7.89 17.10 7.89 7.89 580.31 987.91 580.31 580.31 580.31 987.91 580.31 580.31 7.89 12.15 7.89 7.89 9.19 17.47 9.19 9.19 7.64 11.67 7.64 7.64 9.88 19.58 9.88 9.88 37.40 78.95 37.40 37.40 37.40 78.95 37.40 37.40 10.65 19.54 10.65 10.65 9.45 18.21 9.45 9.45 9.75 16.50 9.75 9.75 9.90 21.45 9.90 9.90 37.32 84.17 37.32 37.32 10.65 19.54 10.65 10.65 9.52 18.83 9.52 9.52 9.95 17.10 9.95 9.95 9.90 21.63 9.90 9.90 37.32 84.17 37.32 37.32 7.89 17.34 7.89 7.89 37.32 84.17 37.32 37.32 5.35 7.81 5.35 5.35 9.29 16.19 9.29 9.29 5.28 7.70 5.28 5.28 9.69 17.16 9.69 9.69 37.28 72.78 37.28 37.28 10.11 17.61 10.11 10.11 11.16 22.15 11.16 11.16 293.18 677.41 293.18 293.18 293.18 677.41 293.18 293.18 37.28 85.42 37.28 37.28 7.89 17.39 7.89 7.89 5.85 8.58 5.85 5.85 8.64 14.87 8.64 8.64 5.59 8.18 5.59 5.59 9.73 17.51 9.73 9.73 37.34 74.21 37.34 37.34 7.90 16.85 7.90 7.90 5.35 7.81 5.35 5.35 5.31 9.42 5.31 5.31 11.42 24.89 11.42 11.42

Power System Studies : HPCL-Nagaon Paper Mill

Short Circuit Study Results Table 4.2 Only Generators (Two TGs) feeding power to the plant Three-Phase & LG, LL, LLG Faults: Bus Information =================== ID kV ------------ -----A+B 11.00 DBB2 11.00 LAGOON 0.41 LCC5 0.41 NA 11.00 NA1 11.00 NB1 11.00 NB2 11.00 NB11 0.41 NB12 0.41 NB13 0.41 NB21 0.41 NB22 0.41 NB23 0.41 NC1 11.00 NC2 11.00 NC11 0.41 NC12 3.30 NC13 0.41 NC21 0.41 NC22 3.30 NC23 0.41 NC_22P 11.00 NC_22S 3.30 ND1 11.00 ND2 11.00 ND11 3.30 ND11_S 3.30 ND12 0.41 ND13 0.41 ND21 3.30 ND21_P 11.00 ND21_S 3.30 ND22 0.41 ND23 0.41 ND_11P 11.00 NE 11.00 NE1 0.41 NE2 0.41 NE3 0.41 NE4_1 0.11 NE4_2 0.11 NF 11.00 NF1 3.30 NF1_P 11.00 NF1_S 3.30 NF2 0.41 NF3 0.41 NG 11.00 NG1 3.30 NG1_P 11.00 NG1_S 3.30 NG2 0.41 NH 11.00 NH1 3.30 NH1_P 11.00 NH1_S 3.30 NH2 0.41 NH3 0.41 NH4 0.41 NI 11.00 NI1 3.30 NI1_P 11.00 NI1_S 3.30 NI2 0.41 NJ 11.00 NK 11.00 NL 11.00 NL1 3.30 NL1_P 11.00 NL1_S 3.30 NL2 0.41 NL3 0.41 NM 11.00 Township 11.00 NK1_1 0.14 NK1_2 0.14 RIVER_WAT 3.30 Nk3 0.41

IV-11

( Prefault Voltage = Bus Nominal Voltage )

3-Phase Fault ==================== I"k ip Ik ------ ------ -----15.55 42.69 3.52 10.86 16.76 3.41 36.24 74.24 36.24 7.86 17.01 7.86 6.04 8.73 3.16 4.03 5.86 2.92 14.41 28.27 3.50 13.71 24.78 3.48 37.50 86.33 37.50 37.50 86.33 37.50 37.50 86.33 37.50 37.39 84.94 37.39 37.39 84.94 37.39 37.39 84.94 37.39 14.41 28.27 3.50 11.82 18.88 3.44 7.91 17.44 7.91 9.91 23.31 9.02 37.50 86.33 37.50 7.89 17.24 7.89 9.32 18.13 8.86 37.10 81.64 37.10 11.09 17.24 3.42 9.62 20.24 8.94 14.07 26.42 3.49 14.07 26.42 3.49 9.56 19.72 8.92 9.82 22.20 8.99 37.45 85.63 37.45 37.45 85.63 37.45 9.61 20.16 8.94 13.49 23.89 3.48 9.83 22.34 9.00 37.45 85.63 37.45 37.45 85.63 37.45 13.34 23.32 3.48 11.82 18.88 3.44 37.10 81.64 37.10 7.89 17.24 7.89 7.89 17.24 7.89 562.141023.82 312.59 562.141023.82 312.59 11.82 18.88 3.44 9.46 19.05 8.90 11.38 17.86 3.43 9.65 20.48 8.95 37.10 81.64 37.10 37.10 81.64 37.10 15.48 40.34 3.52 9.53 19.54 8.92 14.66 29.95 3.50 9.93 23.63 9.02 37.73 89.52 37.73 15.48 40.34 3.52 9.64 20.42 8.95 14.89 31.82 3.51 9.95 23.95 9.03 37.73 89.52 37.73 7.92 17.57 7.92 37.73 89.52 37.73 7.34 10.68 3.26 8.89 16.04 8.73 7.22 10.51 3.25 9.02 16.59 8.77 36.00 72.49 36.00 8.03 11.76 3.30 9.20 13.67 3.35 8.18 12.00 3.31 8.78 15.58 8.70 7.74 11.30 3.28 9.13 17.15 8.80 36.29 74.60 36.29 7.85 16.90 7.85 7.34 10.68 3.26 9.88 14.87 3.38 272.82 518.70 227.73 272.82 518.70 227.73 4.83 8.73 4.83 36.57 76.82 36.57

Line-to-Ground Fault =========================== I"k ip Ib Ik ------ ------ ------ -----1.98 5.43 1.98 1.98 1.91 2.95 1.91 1.91 37.97 77.78 37.97 37.97 7.93 17.17 7.93 7.93 1.73 2.50 1.73 1.73 1.41 2.06 1.41 1.41 1.96 3.85 1.96 1.96 1.95 3.53 1.95 1.95 38.82 89.35 38.82 38.82 38.82 89.35 38.82 38.82 38.82 89.35 38.82 38.82 38.74 88.00 38.74 38.74 38.74 88.00 38.74 38.74 38.74 88.00 38.74 38.74 1.96 3.85 1.96 1.96 1.93 3.08 1.93 1.93 7.96 17.56 7.96 7.96 10.62 25.00 10.62 10.62 38.82 89.35 38.82 38.82 7.95 17.38 7.95 7.95 9.87 19.20 9.87 9.87 38.54 84.82 38.54 38.54 1.92 2.98 1.92 1.92 10.43 21.93 10.43 10.43 1.96 3.68 1.96 1.96 1.96 3.68 1.96 1.96 10.06 20.76 10.06 10.06 10.56 23.88 10.56 10.56 38.78 88.67 38.78 38.78 38.78 88.67 38.78 38.78 10.16 21.30 10.16 10.16 1.95 3.46 1.95 1.95 10.57 24.02 10.57 10.57 38.78 88.67 38.78 38.78 38.78 88.67 38.78 38.78 1.95 3.41 1.95 1.95 1.93 3.08 1.93 1.93 38.54 84.82 38.54 38.54 7.95 17.38 7.95 7.95 7.95 17.38 7.95 7.95 670.191220.59 670.19 670.19 670.191220.59 670.19 670.19 1.93 3.08 1.93 1.93 10.11 20.35 10.11 10.11 1.92 3.02 1.92 1.92 10.45 22.17 10.45 10.45 38.54 84.82 38.54 38.54 38.54 84.82 38.54 38.54 1.98 5.15 1.98 1.98 9.83 20.14 9.83 9.83 1.97 4.02 1.97 1.97 10.64 25.32 10.64 10.64 38.98 92.49 38.98 38.98 1.98 5.15 1.98 1.98 10.03 21.25 10.03 10.03 1.97 4.20 1.97 1.97 10.65 25.65 10.65 10.65 38.98 92.49 38.98 38.98 7.97 17.68 7.97 7.97 38.98 92.49 38.98 38.98 1.81 2.63 1.81 1.81 9.79 17.66 9.79 9.79 1.80 2.62 1.80 1.80 10.01 18.42 10.01 10.01 37.81 76.15 37.81 37.81 1.84 2.69 1.84 1.84 1.87 2.78 1.87 1.87 1.84 2.70 1.84 1.84 9.45 16.78 9.45 9.45 1.82 2.66 1.82 1.82 10.09 18.95 10.09 10.09 38.00 78.12 38.00 38.00 7.93 17.06 7.93 7.93 1.81 2.63 1.81 1.81 1.89 2.85 1.89 1.89 306.23 582.21 306.23 306.23 306.23 582.21 306.23 306.23 5.35 9.67 5.35 5.35 38.19 80.21 38.19 38.19

Line-to-Line Fault =========================== I"k ip Ib Ik ------ ------ ------ -----13.47 36.97 13.47 13.47 9.41 14.51 9.41 9.41 31.39 64.29 31.39 31.39 6.81 14.73 6.81 6.81 5.23 7.56 5.23 5.23 3.49 5.08 3.49 3.49 12.48 24.49 12.48 12.48 11.87 21.46 11.87 11.87 32.48 74.76 32.48 32.48 32.48 74.76 32.48 32.48 32.48 74.76 32.48 32.48 32.38 73.56 32.38 32.38 32.38 73.56 32.38 32.38 32.38 73.56 32.38 32.38 12.48 24.49 12.48 12.48 10.24 16.35 10.24 10.24 6.85 15.10 6.85 6.85 8.58 20.19 8.58 8.58 32.48 74.76 32.48 32.48 6.83 14.93 6.83 6.83 8.07 15.70 8.07 8.07 32.13 70.70 32.13 32.13 9.61 14.93 9.61 9.61 8.33 17.53 8.33 8.33 12.18 22.88 12.18 12.18 12.18 22.88 12.18 12.18 8.28 17.08 8.28 8.28 8.51 19.23 8.51 8.51 32.43 74.16 32.43 32.43 32.43 74.16 32.43 32.43 8.32 17.46 8.32 8.32 11.68 20.69 11.68 11.68 8.52 19.35 8.52 8.52 32.43 74.16 32.43 32.43 32.43 74.16 32.43 32.43 11.55 20.20 11.55 11.55 10.24 16.35 10.24 10.24 32.13 70.70 32.13 32.13 6.83 14.93 6.83 6.83 6.83 14.93 6.83 6.83 486.83 886.65 486.83 486.83 486.83 886.65 486.83 486.83 10.24 16.35 10.24 10.24 8.20 16.49 8.20 8.20 9.85 15.47 9.85 9.85 8.36 17.74 8.36 8.36 32.13 70.70 32.13 32.13 32.13 70.70 32.13 32.13 13.41 34.94 13.41 13.41 8.26 16.92 8.26 8.26 12.70 25.94 12.70 12.70 8.60 20.46 8.60 8.60 32.67 77.53 32.67 32.67 13.41 34.94 13.41 13.41 8.35 17.69 8.35 8.35 12.90 27.55 12.90 12.90 8.61 20.74 8.61 8.61 32.67 77.53 32.67 32.67 6.86 15.21 6.86 6.86 32.67 77.53 32.67 32.67 6.35 9.25 6.35 6.35 7.70 13.89 7.70 7.70 6.26 9.10 6.26 6.26 7.81 14.37 7.81 7.81 31.17 62.78 31.17 31.17 6.96 10.18 6.96 6.96 7.97 11.84 7.97 7.97 7.09 10.39 7.09 7.09 7.60 13.50 7.60 7.60 6.70 9.79 6.70 6.70 7.91 14.85 7.91 7.91 31.43 64.60 31.43 31.43 6.80 14.64 6.80 6.80 6.35 9.25 6.35 6.35 8.56 12.88 8.56 8.56 236.27 449.21 236.27 236.27 236.27 449.21 236.27 236.27 4.18 7.56 4.18 4.18 31.67 66.53 31.67 31.67

All fault currents are in rms kA. Current ip is calculated using Method C. * LLG fault current is the larger of the two faulted line currents.

Line-to-Line-to-Grd* =========================== I"k ip Ib Ik ------ ------ ------ -----13.49 37.03 13.49 13.49 9.70 14.96 9.70 9.70 38.52 78.90 38.52 38.52 7.95 17.19 7.95 7.95 5.57 8.06 5.57 5.57 3.74 5.44 3.74 3.74 12.63 24.78 12.63 12.63 12.06 21.80 12.06 12.06 38.40 88.39 38.40 38.40 38.40 88.39 38.40 38.40 38.40 88.39 38.40 38.40 38.43 87.31 38.43 38.43 38.43 87.31 38.43 38.43 38.43 87.31 38.43 38.43 12.63 24.78 12.63 12.63 10.50 16.78 10.50 10.50 7.94 17.52 7.94 7.94 10.45 24.59 10.45 10.45 38.40 88.39 38.40 38.40 7.94 17.36 7.94 7.94 9.85 19.17 9.85 9.85 38.50 84.72 38.50 38.50 9.89 15.38 9.89 9.89 10.50 22.08 10.50 10.50 12.35 23.19 12.35 12.35 12.35 23.19 12.35 12.35 10.24 21.13 10.24 10.24 10.48 23.68 10.48 10.48 38.42 87.85 38.42 38.42 38.42 87.85 38.42 38.42 10.26 21.51 10.26 10.26 11.88 21.04 11.88 11.88 10.47 23.80 10.47 10.47 38.42 87.85 38.42 38.42 38.42 87.85 38.42 38.42 11.76 20.56 11.76 11.76 10.50 16.78 10.50 10.50 38.50 84.72 38.50 38.50 7.94 17.36 7.94 7.94 7.94 17.36 7.94 7.94 671.731223.40 671.73 671.73 671.731223.40 671.73 671.73 10.50 16.78 10.50 10.50 9.88 19.88 9.88 9.88 10.13 15.91 10.13 10.13 10.50 22.28 10.50 10.50 38.50 84.72 38.50 38.50 38.50 84.72 38.50 38.50 13.45 35.04 13.45 13.45 10.44 21.40 10.44 10.44 12.83 26.20 12.83 12.83 10.44 24.84 10.44 10.44 38.48 91.30 38.48 38.48 13.45 35.04 13.45 13.45 10.52 22.29 10.52 10.52 13.01 27.79 13.01 13.01 10.43 25.10 10.43 10.43 38.48 91.30 38.48 38.48 7.95 17.64 7.95 7.95 38.48 91.30 38.48 38.48 6.70 9.75 6.70 6.70 9.95 17.94 9.95 9.95 6.60 9.60 6.60 6.60 10.37 19.08 10.37 10.37 38.49 77.52 38.49 38.49 7.30 10.68 7.30 7.30 8.29 12.32 8.29 8.29 7.43 10.89 7.43 7.43 9.25 16.42 9.25 9.25 7.05 10.29 7.05 7.05 10.41 19.54 10.41 10.41 38.52 79.18 38.52 38.52 7.95 17.11 7.95 7.95 6.70 9.75 6.70 6.70 8.87 13.35 8.87 8.87 314.06 597.11 314.06 314.06 314.06 597.11 314.06 314.06 5.51 9.98 5.51 5.51 38.53 80.93 38.53 38.53

Power System Studies : HPCL-Nagaon Paper Mill

Table 4.3 Short Circuit Summary Report (With and without Reactor connected at NA and NN feeders) IV-12 (a) Only Generators (Two TGs) feeding power to the plant With Reactor Bus Information 3-Phase Fault Line-to-Ground Fault Line-to-Line Fault Line-to-Line-to-Grd* =================== ==================== =========================== =========================== =========================== ID kV I"k ip Ik I"k ip Ib Ik I"k ip Ib Ik I"k ip Ib Ik ------------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ -----NA 11.00 4.99 7.46 3.06 1.58 2.36 1.58 1.58 4.32 6.46 4.32 4.32 4.56 6.82 4.56 4.56 NA1 11.00 3.51 5.25 2.83 1.32 1.97 1.32 1.32 3.04 4.55 3.04 3.04 3.23 4.83 3.23 3.23 Reactor_NA 11.00 8.13 22.37 3.30 1.77 4.87 1.77 1.77 7.04 19.37 7.04 7.04 7.07 19.45 7.07 7.07 Reactor_NN 11.00 2.23 5.21 2.23 1.12 2.61 1.12 1.12 1.93 4.51 1.93 1.93 1.98 4.63 1.98 1.98 RIVER_WAT 3.30 4.48 8.29 4.48 5.05 9.34 5.05 5.05 3.88 7.18 3.88 3.88 5.14 9.52 5.14 5.14 TOWNSHIP 11.00 2.22 5.02 2.22 1.11 2.52 1.11 1.11 1.92 4.35 1.92 1.92 1.97 4.47 1.97 1.97

Without Reactor Bus Information 3-Phase Fault Line-to-Ground Fault Line-to-Line Fault Line-to-Line-to-Grd* =================== ==================== =========================== =========================== =========================== ID kV I"k ip Ik I"k ip Ib Ik I"k ip Ib Ik I"k ip Ib Ik ------------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ -----NA 11.00 6.04 8.73 3.16 1.73 2.50 1.73 1.73 5.23 7.56 5.23 5.23 5.57 8.06 5.57 5.57 NA1 11.00 4.03 5.86 2.92 1.41 2.06 1.41 1.41 3.49 5.08 3.49 3.49 3.74 5.44 3.74 3.74 RIVER_WAT 3.30 4.83 8.73 4.83 5.35 9.67 5.35 5.35 4.18 7.56 4.18 4.18 5.51 9.98 5.51 5.51 TOWNSHIP 11.00 9.88 14.87 3.38 1.89 2.85 1.89 1.89 8.56 12.88 8.56 8.56 8.87 13.35 8.87 8.87

(b) Both Generators and Grid feeding power to the plant With Reactor Bus Information 3-Phase Fault Line-to-Ground Fault Line-to-Line Fault Line-to-Line-to-Grd* =================== ==================== =========================== =========================== =========================== ID kV I"k ip Ik I"k ip Ib Ik I"k ip Ib Ik I"k ip Ib Ik ------------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ -----NA 11.00 4.09 6.09 4.09 2.90 4.33 2.90 2.90 3.54 5.28 3.54 3.54 4.03 6.01 4.03 4.03 NA1 11.00 3.04 4.53 3.04 2.09 3.12 2.09 2.09 2.63 3.93 2.63 2.63 2.91 4.33 2.91 2.91 Reactor_NA 11.00 6.46 13.59 6.46 6.18 12.99 6.18 6.18 5.60 11.77 5.60 5.60 6.87 14.44 6.87 6.87 Reactor_NN 11.00 2.16 5.89 2.16 2.16 5.89 2.16 2.16 1.87 5.10 1.87 1.87 2.16 5.90 2.16 2.16 RIVER_WAT 3.30 4.25 7.71 4.25 4.86 8.82 4.86 4.86 3.68 6.68 3.68 3.68 4.97 9.01 4.97 4.97 TOWNSHIP 11.00 2.15 5.66 2.15 2.15 5.65 2.15 2.15 1.87 4.91 1.87 1.87 2.18 5.74 2.18 2.18

Without Reactor Bus Information 3-Phase Fault Line-to-Ground Fault Line-to-Line Fault Line-to-Line-to-Grd* =================== ==================== =========================== =========================== =========================== ID kV I"k ip Ik I"k ip Ib Ik I"k ip Ib Ik I"k ip Ib Ik ------------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ -----NA 11.00 4.78 6.93 4.78 3.14 4.55 3.14 3.14 4.14 6.00 4.14 4.14 4.56 6.60 4.56 4.56 NA1 11.00 3.42 4.99 3.42 2.23 3.25 2.23 2.23 2.97 4.32 2.97 2.97 3.20 4.65 3.20 3.20 RIVER_WAT 3.30 4.57 8.10 4.57 5.14 9.11 5.14 5.14 3.96 7.01 3.96 3.96 5.31 9.42 5.31 5.31 TOWNSHIP 11.00 10.86 23.66 10.86 10.56 23.01 10.56 10.56 9.41 20.49 9.41 9.41 11.42 24.89 11.42 11.42

IV-13

Power System Studies : HPCL-Nagaon Paper Mill

Chapter - IV

Short Circuit Study 4.1 Introduction to Short-Circuit Study

Whenever a fault occurs in an electrical power system, relatively high currents flow, producing large amounts of destructive energy in the form of heat and magnetic forces. A short-circuit study is performed to: • • •

Make certain protective devices have adequate interrupting current capability; Ensure power system components can withstand mechanical and thermal stresses that occur during a fault; and Calculate current data for protective device coordination studies.

Computer-based modelling is used to calculate maximum three-phase short-circuit currents which are compared to protective device component short-circuit current ratings. The reliability and safety of electric power distribution systems depend on accurate and thorough knowledge of short-circuit fault currents that can be present, and on the ability of protective devices to satisfactorily interrupt these currents. Knowledge of the computational methods of power system analysis is thus essential to engineers with responsibility for planning, design, operation, and troubleshooting of distribution systems. Such knowledge is necessary to determine the interrupting requirements of circuit breakers and fuses, and the mechanical and thermal requirements of devices exposed to fault currents, as well as to perform protection and coordination studies. Basic analysis concepts are also essential for developing equivalent system impedances used in voltage-drop, motor-starting, and harmonic analyses. 4.2 Types of Short Circuit Faults Various types of short-circuit can occur in electrical installations. The primary characteristics are: • •

•

Duration (self-extinguishing, transient and steady-state); Origin: - Mechanical (break in a conductor, accidental electrical contact between two conductors via a foreign conducting body such as a tool or an animal); - Internal or atmospheric over-voltages; - Insulation breakdown due to heat, humidity or a corrosive environment; Location (inside or outside a machine or an electrical switchyard).

Short-circuit can be: • • •

Phase-to-earth (80% of faults); Phase-to-phase (15% of faults): This type of fault often degenerates into a three-phase fault; Three-phase (only 5% of faults);

IV-1

Power System Studies : HPCL-Nagaon Paper Mill

These different short-circuit currents are shown in figure 4.1 (a)-(d).

L3

L3

L2

L2

L1

L1

Ik”

Fig. 4.1 (a) Symmetrical three-phase short-circuit

Ik”

Fig. 4.1 (b) Phase-to-phase short-circuit

L3

L3

L2

L2

L1

L1

Ik”

Ik”

Ik”

Ik”

Fig. 4.1 (c) Phase-to-phase-to-earth short circuit

Fig. 4.1 (d) Phase-to-earth short-circuit

4.3 System and Equipment Data Short-circuit study requires the following data : Bus Data • Nominal kV (when the pre-fault voltage option is set to use nominal kV) • %V (when the pre-fault voltage option is set to use bus voltage) • Type, such as motor control centre (MCC), switchgear, etc., and continuous and bracing ratings Branch Data • Branch impedance (Z), resistance (R), reactance (X), or reactance to resistance ratio (X/R) values and units, tolerance, and temperatures, if applicable • Cable and transmission line length and unit • Transformer rated kV and MVA • Base kV and MVA of impedance branches

IV-2

Power System Studies : HPCL-Nagaon Paper Mill

Additional data for unbalanced short-circuit calculations includes: • Zero sequence impedances • Transformer winding connections, grounding types, and grounding parameters Utility Data • Nominal kV • %V and Angle • 3-Phase MVAsc and X/R Additional data for unbalanced short-circuit calculations includes: • Grounding types and parameters Synchronous Generator Data • Rated MW, kV, and power factor • Sub-transient reactance (X”), transient reactance (X’), and X/R • Generator type • IEC exciter type Additional data for unbalanced short-circuit calculations includes: • Grounding types and parameters • Zero sequence reactance (X0) Synchronous Motor Data • Rated kW/hp and kV, and the number of poles • X” and X/R • % Locked rotor current (LRC), • direct axis synchronous reactance (Xd) • direct axis transient open circuit time constant (Tdo’) Additional data for unbalanced short-circuit calculations includes: • Grounding types and parameters • Zero sequence reactance (X0) Induction Motor Data • Rated kW/hp and kV • X/R plus one of the following: • % LRC, Xd, and direct axis transient time constant (Td’) Additional data for unbalanced short-circuit calculations includes: • Grounding types and parameters • Zero sequence reactance (X0) Lumped Load Data • Rated MVA and kV • % motor load • % LRC, X/R, and Xsc for .5 cycle and 1.5-4 cycle • X’, X, and Td’ for IEC short-circuit calculation Additional data for unbalanced short-circuit calculations includes: • Grounding types and parameters High Voltage Circuit Breaker Data IEC Standard Circuit Breaker: • Rated kV • Minimum Delay (in second) • Making Current (peak) • AC Breaking current (rms)

IV-3

Power System Studies : HPCL-Nagaon Paper Mill

Low Voltage Circuit Breaker Data IEC Standard Circuit Breaker: • Type (moulded case or insulated case) • Rated kV • Min. Delay (minimum delay time in second) • Making current (peak) • AC Breaking current (rms) Fuse Data IEC Standard Fuse: • AC Breaking current (rms) • Test power factor Note: Circuit Interrupting device data is required to calculate the interrupting capabilities of the circuit breaker, fuse etc. from the rated and maximum interrupting capabilities. This value is calculated at the nominal kV of the bus that the interrupting device is connected to. 4.4 Standard Followed Short-circuit study is performed using IEC-909 Standard, the IEC Calculation Method includes all important results, including initial symmetrical short-circuit current, peak short-circuit current, symmetrical short-circuit breaking current, and steady-state short-circuit currents. Standard Compliance • •

IEC 909-1 (1991) : Short-circuit calculation in three-phase ac systems IEC 909-2 (1988) : Electrical equipment - data for short-circuit current calculations in accordance with IEC-909

The standards are for short-circuit calculation in ac systems and operating at 50 Hz or 60 Hz. They cover three-phase, line-to-ground, line-to-line, and line-to-line-to-ground faults. IEC classifies short-circuit currents according to their magnitudes (maximum and minimum) and their distances from the generator (far and near). Maximum short-circuit currents determine equipment ratings, while minimum currents dictate protective device settings. Near-to-generator and far-from-generator classifications determine whether or not to model the ac component decay, respectively. IEC 363 Standard calculates the short-circuit current as a function of time and displays its instantaneous values using the machine’s sub-transient reactance and time constants. This provides an accurate evaluation of the short-circuit current for sizing protective devices and coordinating relays for isolated systems such as ships and off-shore platforms. IEC Short-Circuit Calculation Method In IEC short-circuit calculations, an equivalent voltage source at the fault location replaces all voltage sources. A voltage factor 'c' is applied to adjust the value of the equivalent voltage source for minimum and maximum current calculations. All machines are represented by their internal impedances. Line capacitances and static loads are neglected, except for those of the zero-sequence system. Regulator and transformer taps are assumed to be in the main position, and arc resistances are not considered. System impedances are assumed to be balanced three-phase, and the method of symmetrical components is used for unbalanced fault calculations.

IV-4

Power System Studies : HPCL-Nagaon Paper Mill

Calculations consider electrical distance from the fault location to synchronous generators. For a far-from-generator fault, calculations assume that the steady-state value of the short-circuit current is equal to the initial symmetrical short-circuit current. Only the dc component decays to zero. Whereas for a near-to-generator fault, calculations account for both decaying ac and dc components. The equivalent R/X ratios determine the rates of decay of both components, and different values are recommended for generators and motors near the fault. Calculations also differ for meshed and unmeshed networks. The factor k, which is used to multiply the initial short-circuit current to get the peak short-circuit current ip, is defined differently for different system configurations and the methods selected to calculate the R/X ratios. Definition of Terms: IEC standards use the following definitions, which are relevant in the calculations of short-circuit currents. Initial Symmetrical Short-Circuit Current (I”k) This is the rms value of the ac symmetrical component of an available short-circuit current applicable at the instant of short-circuit if the impedance remains at zero time value. Peak Short-Circuit Current (ip) This is the maximum possible instantaneous value of the available short-circuit current. Symmetrical Short-Circuit Breaking Current (Ib) This is the rms value of an integral cycle of the symmetrical ac component of the available shortcircuit current at the instant of contact separation of the first pole of a switching device. Steady-State Short-Circuit Current (Ik) This is the rms value of the short-circuit current which remains after the decay of the transient phenomena. Sub-transient Voltage (E”) of a Synchronous Machine This is the rms value of the symmetrical internal voltage of a synchronous machine which is active behind the sub-transient reactance X”d at the moment of short-circuit. Far-From-Generator Short-Circuit This is a short-circuit condition during which the magnitude of the symmetrical ac component of available short-circuit current remains essentially constant. Near-To-Generator Short-Circuit This is a short-circuit condition to which at least one synchronous machine contributes a prospective initial short-circuit current which is more than twice the generator’s rated current, or a short-circuit condition to which synchronous and asynchronous motors contribute more than 5% of the initial symmetrical short-circuit current ( I”k) without motors. Sub-transient Reactance (X”d) of a Synchronous Machine This is the effective reactance at the moment of short-circuit. For the calculation of short-circuit currents, the saturated value of (X”d) is taken. Minimum Time Delay (Tmin) of a Circuit Breaker This is the shortest time between the beginning of the short-circuit current and the first contact separation of one pole of the switching device. Note that the time delay (Tmin) is the sum of the shortest possible operating time of an instantaneous relay and the shortest opening time of a circuit breaker. Minimum time delay does not include the adjustable time delays of tripping devices.

Power System Studies : HPCL-Nagaon Paper Mill

Voltage Factor 'c' This is the factor used to adjust the value of the equivalent voltage source for minimum and maximum current calculations according to the following table:

Factor 'c' IV-5 For Maximum Short-Circuit For Maximum Short-Circuit Current Calculation Current Calculation cmax cmin

Nominal Voltage UN Low Voltage : 100V to 1000V - 230V / 400V - Other Voltages Medium Voltage: > 1kV to 35kV High Voltage: > 35kV to 230kV

1.00 1.05 1.10 1.10

0.95 1.00 1.00 1.00

The cmax values given in the above table are used as default values in calculations and the user can set these values from the Short-Circuit Study Case. Calculation Methods Initial Symmetrical Short-Circuit Current Calculation Initial symmetrical short-circuit current (I”k) is calculated using the following formula:

I k" =

cU n 3Z k

where Zk is the equivalent impedance at the fault location. Peak Short-Circuit Current Calculation Peak short-circuit current (Ip)is calculated using the following formula:

i p = 2kI kn where k is a function of the system R/X ratio at the fault location. IEC standards provide three methods for calculating the k factor: Method A - Uniform ratio R/X. The value of the k factor is determined from taking the smallest ratio of R/X of all the branches of the network. Only branches that contain a total of 80 percent of the current at the nominal voltage corresponding to the short-circuit location are included. Branches may be a series combination of several elements. Method B - R/X ratio at the short-circuit location. The value of the k factor is determined by multiplying the k factor by a safety factor of 1.15, which covers inaccuracies caused after obtaining the R/X ratio from a network reduction with complex impedances. Method C - Equivalent frequency. The value of the k factor is calculated using a frequencyaltered R/X. R/X is calculated at a lower frequency and then multiplied by a frequency-dependent multiplying factor. Symmetrical Short-Circuit Breaking Current Calculation For a far-from-generator fault, the symmetrical short-circuit breaking current (Ib) is equal to the initial symmetrical short-circuit current.

I b = I k" For near-to-generator fault, (Ib) is obtained by combining contributions from each individual machine. (Ib) for different types of machines are calculated using the following formula:

IV-6

Power System Studies : HPCL-Nagaon Paper Mill

µI k" Ib =  µqI k"

for synchronous machine for asynchronous machine

where µ and q are factors that account for ac decay. They are functions of the ratio of the minimum time delay and the ratio of the machine’s initial short-circuit current to its rated current, IV-6machines. as well as real power per pair of poles of asynchronous IEC standard allows to include or exclude ac decay effect from asynchronous machines in the calculation. DC Component of Short-Circuit Current Calculation The dc component of the short-circuit current for the minimum delay time of a protective device, is calculated based on initial symmetrical short-circuit current and system X/R ratio:

I dc = I

" k

 2πft  min  2 exp −  X  R  

where f is the system frequency, tmin is the minimum delay time of the protective device under concern, and X/R is the system value at the faulted bus. Asymmetrical Short-Circuit Breaking Current Calculation The asymmetrical short-circuit breaking current for comparison with circuit breaker rating, is calculated as the rms value of symmetrical and dc components of the short circuit current. For fuses, it is the sum of asymmetrical currents from all first level contribution branches. Steady-State Short-Circuit Current Calculation Steady-state short-circuit current (Ik) is a combination of contributions from synchronous generators. (Ik) for each synchronous generator is calculated using the following formula:

I k max = λmax I rG

I k min = λmin I rG where λ is a function of a generator’s excitation voltage, ratio between its initial symmetrical shortcircuit current and rated current, and other generator parameters, and IrG is the generator’s rated current. The above short-circuit calculation method can be followed for hand calculations in case of simpler network. The main part here is to calculate the equivalent impedance of the network at the fault locations. From the one line diagram representation of the network with its elements represented in the form of impedance, the equivalent impedance is calculated using network reduction technique. However in case of complex network the calculation becomes too tedious and time consuming to do manually. Hence computer program is used wherein only One Line Diagram with network parameters are required and rest all calculations as per IEC-909 are taken care of automatically. The maximum steady-state current reflects maximum modelling inaccuracies. This value is used to determine minimum device ratings. The minimum steady-state current reflects minimum modelling inaccuracies. This value is used for relay coordination purposes in preventing the occurrence of nuisance trips and loading deviations.

Power System Studies : HPCL-Nagaon Paper Mill

4.5 Short Circuit Studies Short-circuit analysis for HPCL-Nagaon Paper Mill is carried out using Short-Circuit Computer Program in accordance with IEC-909 guidelines. The entire plant power system network was represented in the form of One Line Diagram representing the various components such as Grid, Generators, Transformers, Cables, Overhead Lines, Motors, Switches (Circuit Breakers), etc. The types of faults considered are : • • • •

3-Phase Fault Line-to-Ground Fault Line-to-Line Fault Line-to-Line-to-Ground

The major operating conditions of the plant considered are : • •

Both the Generators feeding power to the plant Only Grid feeding power to the plant

In the HPCL-NPM system there are reactors connected in the feeder to limit the fault current. In order to ascertain their requirement in the feeders the above short-circuit calculations are also carried out with and without the reactors in NN and NA feeders. The short circuit results of the above cases are shown in the tables 4.1, 4.2 and 4.3 respectively. 4.6 Reduction of Fault Current To limit the current flow in the event of short-circuit current limiting reactor can be used. A current limiting reactor is an inductive coil having a large inductive reactance (ωL), and is used for limiting short-circuit currents to be interrupted by circuit breakers. If X is the reactance of a circuit, E is the voltage, neglecting the resistance, the short circuit current Isc is given by E/X. Therefore by increasing reactance, X of the system, the short circuit currents can be decreased. The short-circuit current depends upon the generating capacity, voltage at the fault point and the total reactance between the generators and the fault point. The circuit breakers should have enough breaking current capacity such that the fault currents are less than the breaking current capacity. If the fault current are beyond the capacity of the circuit breaker, the circuit breaker, may not interrupt the fault current. In a system where several generating stations are interconnected by short feeders, the fault currents can be high, the circuit breakers of suitable breaking capacity may not be available. The fault current, then, should be limited by some means so that available or existing circuit breakers can be used safely. Further, when the system is extended by adding more generating stations or more generator units, the fault current to be interrupted by the same circuit breaker will be greater than before. In such a case the circuit breaker should be replaced by the one with higher breaking current capacity or the fault current can be limited by means of reactors. By including a reactor or a few reactors at strategic locations, the short circuit current at several point can be reduced. Hence current limiting reactors are useful in limiting short-circuit current so that the circuit breaker can interrupt them. However the voltage drop and losses caused by reactors should be within the permissible limits. From the short-circuit study results, it is clear that the fault currents are not so high particularly in NA (River Intake) and NN (Township) feeders. Further reduction of short circuit current in feeders by reactor may lead to relay not getting enough current for its operation during fault. Also the

Power System Studies : HPCL-Nagaon Paper Mill

reactor will cause more voltage drop in the feeder. Hence there is no requirement of any reactor in the NA and NN feeders.

IV-10

Power System Studies : HPCL-Nagaon Paper Mill

Short Circuit Study Results Table 4.1 : Both Generators and Grid feeding power to the plant Three-Phase & LG, LL, LLG Faults: Bus Information =================== ID kV ------------ -----A+B 11.00 ASEB 132.00 BUS C 11.00 DBB1 11.00 DBB2 11.00 LAGOON 0.41 NA 11.00 NA1 11.00 NB1 11.00 NB2 11.00 NB11 0.41 NB12 0.41 NB13 0.41 NB21 0.41 NB22 0.41 NB23 0.41 NC1 11.00 NC2 11.00 NC11 0.41 NC12 3.30 NC13 0.41 NC21 0.41 NC22 3.30 NC23 0.41 NC_22P 11.00 NC_22S 3.30 ND1 11.00 ND2 11.00 ND11 3.30 ND11_S 3.30 ND12 0.41 ND13 0.41 ND21 3.30 ND21_P 11.00 ND21_S 3.30 ND22 0.41 ND23 0.41 ND_11P 11.00 NE 11.00 NE1 0.41 NE2 0.41 NE3 0.41 NE4_1 0.11 NE4_2 0.11 NF 11.00 NF1 3.30 NF1_P 11.00 NF1_S 3.30 NF2 0.41 NF3 0.41 NG 11.00 NG1 3.30 NG1_P 11.00 NG1_S 3.30 NG2 0.41 NH 11.00 NH1 3.30 NH1_P 11.00 NH1_S 3.30 NH2 0.41 NH3 0.41 NH4 0.41 NI 11.00 NI1 3.30 NI1_P 11.00 NI1_S 3.30 NI2 0.41 NJ 11.00 NK 11.00 NK1_1 0.14 NK1_2 0.14 NK2 0.41 NK3 0.41 NL 11.00 NL1 3.30 NL1_P 11.00 NL1_S 3.30 NL2 0.41 NL3 0.41 NM 11.00 RIVER_WAT 3.30 TOWNSHIP 11.00

( Prefault Voltage = Bus Nominal Voltage )

3-Phase Fault ==================== I"k ip Ik ------ ------ -----10.16 18.97 10.16 31.50 77.77 31.50 11.20 28.71 11.20 10.16 18.97 10.16 11.19 28.46 11.19 35.88 79.85 35.88 4.78 6.93 4.78 3.42 4.99 3.42 9.18 15.32 9.18 8.78 14.22 8.78 35.75 78.51 35.75 35.75 78.51 35.75 35.75 78.51 35.75 35.64 77.35 35.64 35.64 77.35 35.64 35.64 77.35 35.64 9.18 15.32 9.18 7.83 12.06 7.83 7.82 17.09 7.82 9.02 19.36 9.02 35.75 78.51 35.75 7.80 16.90 7.80 8.43 15.60 8.43 35.33 74.57 35.33 7.48 11.37 7.48 8.72 17.15 8.72 8.98 14.75 8.98 8.98 14.75 8.98 8.66 16.77 8.66 8.93 18.57 8.93 35.69 77.92 35.69 35.69 77.92 35.69 8.71 17.10 8.71 8.66 13.92 8.66 8.94 18.67 8.94 35.69 77.92 35.69 35.69 77.92 35.69 8.58 13.73 8.58 7.83 12.06 7.83 35.33 74.57 35.33 7.80 16.90 7.80 7.80 16.90 7.80 455.22 774.95 455.22 455.22 774.95 455.22 7.83 12.06 7.83 8.57 16.28 8.57 7.62 11.63 7.62 8.75 17.33 8.75 35.33 74.57 35.33 35.33 74.57 35.33 10.05 18.45 10.05 8.63 16.64 8.63 9.34 15.81 9.34 9.04 19.58 9.04 36.00 81.18 36.00 10.05 18.45 10.05 8.74 17.29 8.74 9.50 16.33 9.50 9.07 19.81 9.07 36.00 81.18 36.00 7.84 17.22 7.84 36.00 81.18 36.00 5.55 8.09 5.55 8.04 14.02 8.04 5.48 7.99 5.48 8.15 14.44 8.15 34.22 66.81 34.22 9.63 16.76 9.63 10.50 20.84 10.50 267.48 618.03 267.48 267.48 618.03 267.48 36.13 82.77 36.13 7.84 17.29 7.84 6.01 8.82 6.01 7.94 13.67 7.94 5.77 8.44 5.77 8.26 14.86 8.26 34.51 68.60 34.51 7.77 16.58 7.77 5.55 8.09 5.55 4.57 8.10 4.57 10.86 23.66 10.86

Line-to-Ground Fault =========================== I"k ip Ib Ik ------ ------ ------ -----9.23 17.23 9.23 9.23 31.50 77.77 31.50 31.50 11.20 28.71 11.20 11.20 9.23 17.23 9.23 9.23 11.19 28.44 11.19 11.19 37.65 83.79 37.65 37.65 3.14 4.55 3.14 3.14 2.23 3.25 2.23 2.23 7.64 12.75 7.64 7.64 7.08 11.47 7.08 7.08 37.56 82.48 37.56 37.56 37.56 82.48 37.56 37.56 37.56 82.48 37.56 37.56 37.48 81.35 37.48 37.48 37.48 81.35 37.48 37.48 37.48 81.35 37.48 37.48 7.64 12.75 7.64 7.64 5.92 9.12 5.92 5.92 7.91 17.28 7.91 7.91 9.94 21.34 9.94 9.94 37.56 82.48 37.56 37.56 7.89 17.09 7.89 7.89 9.18 16.98 9.18 9.18 37.27 78.67 37.27 37.27 5.54 8.42 5.54 5.54 9.73 19.13 9.73 9.73 7.36 12.08 7.36 7.36 7.36 12.08 7.36 7.36 9.36 18.14 9.36 9.36 9.87 20.54 9.87 9.87 37.52 81.91 37.52 37.52 37.52 81.91 37.52 37.52 9.45 18.55 9.45 9.45 6.93 11.13 6.93 6.93 9.88 20.64 9.88 9.88 37.52 81.91 37.52 37.52 37.52 81.91 37.52 37.52 6.83 10.92 6.83 6.83 5.92 9.12 5.92 5.92 37.27 78.67 37.27 37.27 7.89 17.09 7.89 7.89 7.89 17.09 7.89 7.89 566.98 965.20 566.98 566.98 566.98 965.20 566.98 566.98 5.92 9.12 5.92 5.92 9.41 17.88 9.41 9.41 5.69 8.69 5.69 5.69 9.75 19.31 9.75 9.75 37.27 78.67 37.27 37.27 37.27 78.67 37.27 37.27 9.03 16.57 9.03 9.03 9.14 17.62 9.14 9.14 7.88 13.33 7.88 7.88 9.96 21.56 9.96 9.96 37.73 85.09 37.73 37.73 9.03 16.57 9.03 9.03 9.34 18.46 9.34 9.34 8.12 13.96 8.12 8.12 9.97 21.79 9.97 9.97 37.73 85.09 37.73 37.73 7.92 17.39 7.92 7.92 37.73 85.09 37.73 37.73 3.74 5.46 3.74 3.74 9.10 15.87 9.10 9.10 3.69 5.38 3.69 3.69 9.32 16.50 9.32 9.32 36.53 71.31 36.53 36.53 8.32 14.49 8.32 8.32 9.86 19.56 9.86 9.86 299.80 692.71 299.80 299.80 299.80 692.71 299.80 299.80 37.82 86.66 37.82 37.82 7.92 17.46 7.92 7.92 4.14 6.07 4.14 4.14 8.79 15.13 8.79 8.79 3.93 5.75 3.93 3.93 9.39 16.90 9.39 9.39 36.73 73.00 36.73 36.73 7.87 16.79 7.87 7.87 3.74 5.46 3.74 3.74 5.14 9.11 5.14 5.14 10.56 23.01 10.56 10.56

Line-to-Line Fault =========================== I"k ip Ib Ik ------ ------ ------ -----8.80 16.43 8.80 8.80 27.28 67.35 27.28 27.28 9.70 24.86 9.70 9.70 8.80 16.43 8.80 8.80 9.69 24.64 9.69 9.69 31.07 69.15 31.07 31.07 4.14 6.00 4.14 4.14 2.97 4.32 2.97 2.97 7.95 13.27 7.95 7.95 7.60 12.31 7.60 7.60 30.96 67.99 30.96 30.96 30.96 67.99 30.96 30.96 30.96 67.99 30.96 30.96 30.86 66.98 30.86 30.86 30.86 66.98 30.86 30.86 30.86 66.98 30.86 30.86 7.95 13.27 7.95 7.95 6.78 10.44 6.78 6.78 6.78 14.80 6.78 6.78 7.81 16.77 7.81 7.81 30.96 67.99 30.96 30.96 6.76 14.63 6.76 6.76 7.30 13.51 7.30 7.30 30.60 64.58 30.60 30.60 6.48 9.84 6.48 6.48 7.55 14.86 7.55 7.55 7.78 12.77 7.78 7.78 7.78 12.77 7.78 7.78 7.50 14.53 7.50 7.50 7.73 16.08 7.73 7.73 30.91 67.48 30.91 30.91 30.91 67.48 30.91 30.91 7.54 14.81 7.54 7.54 7.50 12.06 7.50 7.50 7.74 16.17 7.74 7.74 30.91 67.48 30.91 30.91 30.91 67.48 30.91 30.91 7.43 11.89 7.43 7.43 6.78 10.44 6.78 6.78 30.60 64.58 30.60 30.60 6.76 14.63 6.76 6.76 6.76 14.63 6.76 6.76 394.23 671.13 394.23 394.23 394.23 671.13 394.23 394.23 6.78 10.44 6.78 6.78 7.42 14.10 7.42 7.42 6.60 10.08 6.60 6.60 7.58 15.01 7.58 7.58 30.60 64.58 30.60 30.60 30.60 64.58 30.60 30.60 8.70 15.97 8.70 8.70 7.48 14.41 7.48 7.48 8.09 13.69 8.09 8.09 7.83 16.96 7.83 7.83 31.17 70.31 31.17 31.17 8.70 15.97 8.70 8.70 7.57 14.97 7.57 7.57 8.23 14.14 8.23 8.23 7.85 17.15 7.85 7.85 31.17 70.31 31.17 31.17 6.79 14.91 6.79 6.79 31.17 70.31 31.17 31.17 4.80 7.01 4.80 4.80 6.96 12.14 6.96 6.96 4.75 6.92 4.75 4.75 7.06 12.51 7.06 7.06 29.64 57.86 29.64 29.64 8.34 14.52 8.34 8.34 9.09 18.05 9.09 9.09 231.64 535.23 231.64 231.64 231.64 535.23 231.64 231.64 31.29 71.68 31.29 31.29 6.79 14.97 6.79 6.79 5.21 7.64 5.21 5.21 6.88 11.84 6.88 6.88 5.00 7.31 5.00 5.00 7.15 12.87 7.15 7.15 29.89 59.41 29.89 29.89 6.73 14.35 6.73 6.73 4.80 7.01 4.80 4.80 3.96 7.01 3.96 3.96 9.41 20.49 9.41 9.41

All fault currents are in rms kA. Current ip is calculated using Method C. * LLG fault current is the larger of the two faulted line currents.

Line-to-Line-to-Grd* =========================== I"k ip Ib Ik ------ ------ ------ -----10.79 20.13 10.79 10.79 31.50 77.77 31.50 31.50 11.20 28.71 11.20 11.20 10.79 20.13 10.79 10.79 11.23 28.55 11.23 11.23 37.35 83.11 37.35 37.35 4.56 6.60 4.56 4.56 3.20 4.65 3.20 3.20 9.54 15.92 9.54 9.54 9.04 14.64 9.04 9.04 37.37 82.06 37.37 37.37 37.37 82.06 37.37 37.37 37.37 82.06 37.37 37.37 37.38 81.14 37.38 37.38 37.38 81.14 37.38 37.38 37.38 81.14 37.38 37.38 9.54 15.92 9.54 9.54 7.89 12.15 7.89 7.89 7.89 17.24 7.89 7.89 9.91 21.26 9.91 9.91 37.37 82.06 37.37 37.37 7.89 17.10 7.89 7.89 8.93 16.52 8.93 8.93 37.40 78.95 37.40 37.40 7.48 11.37 7.48 7.48 9.88 19.43 9.88 9.88 9.29 15.26 9.29 9.29 9.29 15.26 9.29 9.29 9.27 17.96 9.27 9.27 9.91 20.61 9.91 9.91 37.38 81.60 37.38 37.38 37.38 81.60 37.38 37.38 9.28 18.22 9.28 9.28 8.89 14.29 8.89 8.89 9.91 20.69 9.91 9.91 37.38 81.60 37.38 37.38 37.38 81.60 37.38 37.38 8.80 14.07 8.80 8.80 7.89 12.15 7.89 7.89 37.40 78.95 37.40 37.40 7.89 17.10 7.89 7.89 7.89 17.10 7.89 7.89 580.31 987.91 580.31 580.31 580.31 987.91 580.31 580.31 7.89 12.15 7.89 7.89 9.19 17.47 9.19 9.19 7.64 11.67 7.64 7.64 9.88 19.58 9.88 9.88 37.40 78.95 37.40 37.40 37.40 78.95 37.40 37.40 10.65 19.54 10.65 10.65 9.45 18.21 9.45 9.45 9.75 16.50 9.75 9.75 9.90 21.45 9.90 9.90 37.32 84.17 37.32 37.32 10.65 19.54 10.65 10.65 9.52 18.83 9.52 9.52 9.95 17.10 9.95 9.95 9.90 21.63 9.90 9.90 37.32 84.17 37.32 37.32 7.89 17.34 7.89 7.89 37.32 84.17 37.32 37.32 5.35 7.81 5.35 5.35 9.29 16.19 9.29 9.29 5.28 7.70 5.28 5.28 9.69 17.16 9.69 9.69 37.28 72.78 37.28 37.28 10.11 17.61 10.11 10.11 11.16 22.15 11.16 11.16 293.18 677.41 293.18 293.18 293.18 677.41 293.18 293.18 37.28 85.42 37.28 37.28 7.89 17.39 7.89 7.89 5.85 8.58 5.85 5.85 8.64 14.87 8.64 8.64 5.59 8.18 5.59 5.59 9.73 17.51 9.73 9.73 37.34 74.21 37.34 37.34 7.90 16.85 7.90 7.90 5.35 7.81 5.35 5.35 5.31 9.42 5.31 5.31 11.42 24.89 11.42 11.42

Power System Studies : HPCL-Nagaon Paper Mill

Short Circuit Study Results Table 4.2 Only Generators (Both TGs) feeding power toIV-11 the plant Three-Phase & LG, LL, LLG Faults: Bus Information =================== ID kV ------------ -----A+B 11.00 DBB2 11.00 LAGOON 0.41 LCC5 0.41 NA 11.00 NA1 11.00 NB1 11.00 NB2 11.00 NB11 0.41 NB12 0.41 NB13 0.41 NB21 0.41 NB22 0.41 NB23 0.41 NC1 11.00 NC2 11.00 NC11 0.41 NC12 3.30 NC13 0.41 NC21 0.41 NC22 3.30 NC23 0.41 NC_22P 11.00 NC_22S 3.30 ND1 11.00 ND2 11.00 ND11 3.30 ND11_S 3.30 ND12 0.41 ND13 0.41 ND21 3.30 ND21_P 11.00 ND21_S 3.30 ND22 0.41 ND23 0.41 ND_11P 11.00 NE 11.00 NE1 0.41 NE2 0.41 NE3 0.41 NE4_1 0.11 NE4_2 0.11 NF 11.00 NF1 3.30 NF1_P 11.00 NF1_S 3.30 NF2 0.41 NF3 0.41 NG 11.00 NG1 3.30 NG1_P 11.00 NG1_S 3.30 NG2 0.41 NH 11.00 NH1 3.30 NH1_P 11.00 NH1_S 3.30 NH2 0.41 NH3 0.41 NH4 0.41 NI 11.00 NI1 3.30 NI1_P 11.00 NI1_S 3.30 NI2 0.41 NJ 11.00 NK 11.00 NL 11.00 NL1 3.30 NL1_P 11.00 NL1_S 3.30 NL2 0.41 NL3 0.41 NM 11.00 Township 11.00 NK1_1 0.14 NK1_2 0.14 RIVER_WAT 3.30 Nk3 0.41

( Prefault Voltage = Bus Nominal Voltage )

3-Phase Fault ==================== I"k ip Ik ------ ------ -----15.55 42.69 3.52 10.86 16.76 3.41 36.24 74.24 36.24 7.86 17.01 7.86 6.04 8.73 3.16 4.03 5.86 2.92 14.41 28.27 3.50 13.71 24.78 3.48 37.50 86.33 37.50 37.50 86.33 37.50 37.50 86.33 37.50 37.39 84.94 37.39 37.39 84.94 37.39 37.39 84.94 37.39 14.41 28.27 3.50 11.82 18.88 3.44 7.91 17.44 7.91 9.91 23.31 9.02 37.50 86.33 37.50 7.89 17.24 7.89 9.32 18.13 8.86 37.10 81.64 37.10 11.09 17.24 3.42 9.62 20.24 8.94 14.07 26.42 3.49 14.07 26.42 3.49 9.56 19.72 8.92 9.82 22.20 8.99 37.45 85.63 37.45 37.45 85.63 37.45 9.61 20.16 8.94 13.49 23.89 3.48 9.83 22.34 9.00 37.45 85.63 37.45 37.45 85.63 37.45 13.34 23.32 3.48 11.82 18.88 3.44 37.10 81.64 37.10 7.89 17.24 7.89 7.89 17.24 7.89 562.141023.82 312.59 562.141023.82 312.59 11.82 18.88 3.44 9.46 19.05 8.90 11.38 17.86 3.43 9.65 20.48 8.95 37.10 81.64 37.10 37.10 81.64 37.10 15.48 40.34 3.52 9.53 19.54 8.92 14.66 29.95 3.50 9.93 23.63 9.02 37.73 89.52 37.73 15.48 40.34 3.52 9.64 20.42 8.95 14.89 31.82 3.51 9.95 23.95 9.03 37.73 89.52 37.73 7.92 17.57 7.92 37.73 89.52 37.73 7.34 10.68 3.26 8.89 16.04 8.73 7.22 10.51 3.25 9.02 16.59 8.77 36.00 72.49 36.00 8.03 11.76 3.30 9.20 13.67 3.35 8.18 12.00 3.31 8.78 15.58 8.70 7.74 11.30 3.28 9.13 17.15 8.80 36.29 74.60 36.29 7.85 16.90 7.85 7.34 10.68 3.26 9.88 14.87 3.38 272.82 518.70 227.73 272.82 518.70 227.73 4.83 8.73 4.83 36.57 76.82 36.57

Line-to-Ground Fault =========================== I"k ip Ib Ik ------ ------ ------ -----1.98 5.43 1.98 1.98 1.91 2.95 1.91 1.91 37.97 77.78 37.97 37.97 7.93 17.17 7.93 7.93 1.73 2.50 1.73 1.73 1.41 2.06 1.41 1.41 1.96 3.85 1.96 1.96 1.95 3.53 1.95 1.95 38.82 89.35 38.82 38.82 38.82 89.35 38.82 38.82 38.82 89.35 38.82 38.82 38.74 88.00 38.74 38.74 38.74 88.00 38.74 38.74 38.74 88.00 38.74 38.74 1.96 3.85 1.96 1.96 1.93 3.08 1.93 1.93 7.96 17.56 7.96 7.96 10.62 25.00 10.62 10.62 38.82 89.35 38.82 38.82 7.95 17.38 7.95 7.95 9.87 19.20 9.87 9.87 38.54 84.82 38.54 38.54 1.92 2.98 1.92 1.92 10.43 21.93 10.43 10.43 1.96 3.68 1.96 1.96 1.96 3.68 1.96 1.96 10.06 20.76 10.06 10.06 10.56 23.88 10.56 10.56 38.78 88.67 38.78 38.78 38.78 88.67 38.78 38.78 10.16 21.30 10.16 10.16 1.95 3.46 1.95 1.95 10.57 24.02 10.57 10.57 38.78 88.67 38.78 38.78 38.78 88.67 38.78 38.78 1.95 3.41 1.95 1.95 1.93 3.08 1.93 1.93 38.54 84.82 38.54 38.54 7.95 17.38 7.95 7.95 7.95 17.38 7.95 7.95 670.191220.59 670.19 670.19 670.191220.59 670.19 670.19 1.93 3.08 1.93 1.93 10.11 20.35 10.11 10.11 1.92 3.02 1.92 1.92 10.45 22.17 10.45 10.45 38.54 84.82 38.54 38.54 38.54 84.82 38.54 38.54 1.98 5.15 1.98 1.98 9.83 20.14 9.83 9.83 1.97 4.02 1.97 1.97 10.64 25.32 10.64 10.64 38.98 92.49 38.98 38.98 1.98 5.15 1.98 1.98 10.03 21.25 10.03 10.03 1.97 4.20 1.97 1.97 10.65 25.65 10.65 10.65 38.98 92.49 38.98 38.98 7.97 17.68 7.97 7.97 38.98 92.49 38.98 38.98 1.81 2.63 1.81 1.81 9.79 17.66 9.79 9.79 1.80 2.62 1.80 1.80 10.01 18.42 10.01 10.01 37.81 76.15 37.81 37.81 1.84 2.69 1.84 1.84 1.87 2.78 1.87 1.87 1.84 2.70 1.84 1.84 9.45 16.78 9.45 9.45 1.82 2.66 1.82 1.82 10.09 18.95 10.09 10.09 38.00 78.12 38.00 38.00 7.93 17.06 7.93 7.93 1.81 2.63 1.81 1.81 1.89 2.85 1.89 1.89 306.23 582.21 306.23 306.23 306.23 582.21 306.23 306.23 5.35 9.67 5.35 5.35 38.19 80.21 38.19 38.19

Line-to-Line Fault =========================== I"k ip Ib Ik ------ ------ ------ -----13.47 36.97 13.47 13.47 9.41 14.51 9.41 9.41 31.39 64.29 31.39 31.39 6.81 14.73 6.81 6.81 5.23 7.56 5.23 5.23 3.49 5.08 3.49 3.49 12.48 24.49 12.48 12.48 11.87 21.46 11.87 11.87 32.48 74.76 32.48 32.48 32.48 74.76 32.48 32.48 32.48 74.76 32.48 32.48 32.38 73.56 32.38 32.38 32.38 73.56 32.38 32.38 32.38 73.56 32.38 32.38 12.48 24.49 12.48 12.48 10.24 16.35 10.24 10.24 6.85 15.10 6.85 6.85 8.58 20.19 8.58 8.58 32.48 74.76 32.48 32.48 6.83 14.93 6.83 6.83 8.07 15.70 8.07 8.07 32.13 70.70 32.13 32.13 9.61 14.93 9.61 9.61 8.33 17.53 8.33 8.33 12.18 22.88 12.18 12.18 12.18 22.88 12.18 12.18 8.28 17.08 8.28 8.28 8.51 19.23 8.51 8.51 32.43 74.16 32.43 32.43 32.43 74.16 32.43 32.43 8.32 17.46 8.32 8.32 11.68 20.69 11.68 11.68 8.52 19.35 8.52 8.52 32.43 74.16 32.43 32.43 32.43 74.16 32.43 32.43 11.55 20.20 11.55 11.55 10.24 16.35 10.24 10.24 32.13 70.70 32.13 32.13 6.83 14.93 6.83 6.83 6.83 14.93 6.83 6.83 486.83 886.65 486.83 486.83 486.83 886.65 486.83 486.83 10.24 16.35 10.24 10.24 8.20 16.49 8.20 8.20 9.85 15.47 9.85 9.85 8.36 17.74 8.36 8.36 32.13 70.70 32.13 32.13 32.13 70.70 32.13 32.13 13.41 34.94 13.41 13.41 8.26 16.92 8.26 8.26 12.70 25.94 12.70 12.70 8.60 20.46 8.60 8.60 32.67 77.53 32.67 32.67 13.41 34.94 13.41 13.41 8.35 17.69 8.35 8.35 12.90 27.55 12.90 12.90 8.61 20.74 8.61 8.61 32.67 77.53 32.67 32.67 6.86 15.21 6.86 6.86 32.67 77.53 32.67 32.67 6.35 9.25 6.35 6.35 7.70 13.89 7.70 7.70 6.26 9.10 6.26 6.26 7.81 14.37 7.81 7.81 31.17 62.78 31.17 31.17 6.96 10.18 6.96 6.96 7.97 11.84 7.97 7.97 7.09 10.39 7.09 7.09 7.60 13.50 7.60 7.60 6.70 9.79 6.70 6.70 7.91 14.85 7.91 7.91 31.43 64.60 31.43 31.43 6.80 14.64 6.80 6.80 6.35 9.25 6.35 6.35 8.56 12.88 8.56 8.56 236.27 449.21 236.27 236.27 236.27 449.21 236.27 236.27 4.18 7.56 4.18 4.18 31.67 66.53 31.67 31.67

All fault currents are in rms kA. Current ip is calculated using Method C. * LLG fault current is the larger of the two faulted line currents.

IV-12

Line-to-Line-to-Grd* =========================== I"k ip Ib Ik ------ ------ ------ -----13.49 37.03 13.49 13.49 9.70 14.96 9.70 9.70 38.52 78.90 38.52 38.52 7.95 17.19 7.95 7.95 5.57 8.06 5.57 5.57 3.74 5.44 3.74 3.74 12.63 24.78 12.63 12.63 12.06 21.80 12.06 12.06 38.40 88.39 38.40 38.40 38.40 88.39 38.40 38.40 38.40 88.39 38.40 38.40 38.43 87.31 38.43 38.43 38.43 87.31 38.43 38.43 38.43 87.31 38.43 38.43 12.63 24.78 12.63 12.63 10.50 16.78 10.50 10.50 7.94 17.52 7.94 7.94 10.45 24.59 10.45 10.45 38.40 88.39 38.40 38.40 7.94 17.36 7.94 7.94 9.85 19.17 9.85 9.85 38.50 84.72 38.50 38.50 9.89 15.38 9.89 9.89 10.50 22.08 10.50 10.50 12.35 23.19 12.35 12.35 12.35 23.19 12.35 12.35 10.24 21.13 10.24 10.24 10.48 23.68 10.48 10.48 38.42 87.85 38.42 38.42 38.42 87.85 38.42 38.42 10.26 21.51 10.26 10.26 11.88 21.04 11.88 11.88 10.47 23.80 10.47 10.47 38.42 87.85 38.42 38.42 38.42 87.85 38.42 38.42 11.76 20.56 11.76 11.76 10.50 16.78 10.50 10.50 38.50 84.72 38.50 38.50 7.94 17.36 7.94 7.94 7.94 17.36 7.94 7.94 671.731223.40 671.73 671.73 671.731223.40 671.73 671.73 10.50 16.78 10.50 10.50 9.88 19.88 9.88 9.88 10.13 15.91 10.13 10.13 10.50 22.28 10.50 10.50 38.50 84.72 38.50 38.50 38.50 84.72 38.50 38.50 13.45 35.04 13.45 13.45 10.44 21.40 10.44 10.44 12.83 26.20 12.83 12.83 10.44 24.84 10.44 10.44 38.48 91.30 38.48 38.48 13.45 35.04 13.45 13.45 10.52 22.29 10.52 10.52 13.01 27.79 13.01 13.01 10.43 25.10 10.43 10.43 38.48 91.30 38.48 38.48 7.95 17.64 7.95 7.95 38.48 91.30 38.48 38.48 6.70 9.75 6.70 6.70 9.95 17.94 9.95 9.95 6.60 9.60 6.60 6.60 10.37 19.08 10.37 10.37 38.49 77.52 38.49 38.49 7.30 10.68 7.30 7.30 8.29 12.32 8.29 8.29 7.43 10.89 7.43 7.43 9.25 16.42 9.25 9.25 7.05 10.29 7.05 7.05 10.41 19.54 10.41 10.41 38.52 79.18 38.52 38.52 7.95 17.11 7.95 7.95 6.70 9.75 6.70 6.70 8.87 13.35 8.87 8.87 314.06 597.11 314.06 314.06 314.06 597.11 314.06 314.06 5.51 9.98 5.51 5.51 38.53 80.93 38.53 38.53

Power System Studies : HPCL-Nagaon Paper Mill

Table 4.3 Short Circuit Summary Report (With and without Reactor connected at NJ and NA)

(a) Only Generators (Both the TGs) feeding power to the plant With Reactor Bus Information 3-Phase Fault Line-to-Ground Fault Line-to-Line Fault Line-to-Line-to-Grd* =================== ==================== =========================== =========================== =========================== ID kV I"k ip Ik I"k ip Ib Ik I"k ip Ib Ik I"k ip Ib Ik ------------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ -----LAGOON 0.41 23.79 53.40 23.79 27.77 62.35 27.77 27.77 20.60 46.25 20.60 20.60 26.78 60.12 26.78 26.78 NA 11.00 4.98 7.44 3.06 1.58 2.36 1.58 1.58 4.31 6.44 4.31 4.31 4.56 6.81 4.56 4.56 NA1 11.00 3.51 5.24 2.83 1.32 1.96 1.32 1.32 3.04 4.54 3.04 3.04 3.23 4.82 3.23 3.23 NJ 11.00 2.18 4.63 2.18 1.10 2.34 1.10 1.10 1.89 4.01 1.89 1.89 1.94 4.13 1.94 1.94 Reactor_NA 11.00 8.13 22.22 3.30 1.77 4.84 1.77 1.77 7.04 19.24 7.04 7.04 7.07 19.32 7.07 7.07 Reactor_NJ 11.00 2.23 5.21 2.23 1.12 2.61 1.12 1.12 1.93 4.51 1.93 1.93 1.98 4.63 1.98 1.98 RIVER_WAT 3.30 4.47 8.28 4.47 5.05 9.34 5.05 5.05 3.87 7.17 3.87 3.87 5.14 9.51 5.14 5.14

Without Reactor Bus Information 3-Phase Fault Line-to-Ground Fault Line-to-Line Fault Line-to-Line-to-Grd* =================== ==================== =========================== =========================== =========================== ID kV I"k ip Ik I"k ip Ib Ik I"k ip Ib Ik I"k ip Ib Ik ------------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ -----LAGOON 0.41 36.24 74.24 36.24 37.97 77.78 37.97 37.97 31.39 64.29 31.39 31.39 38.52 78.90 38.52 38.52 NA 11.00 6.04 8.73 3.16 1.73 2.50 1.73 1.73 5.23 7.56 5.23 5.23 5.57 8.06 5.57 5.57 NA1 11.00 4.03 5.86 2.92 1.41 2.06 1.41 1.41 3.49 5.08 3.49 3.49 3.74 5.44 3.74 3.74 NJ 11.00 8.03 11.76 3.30 1.84 2.69 1.84 1.84 6.96 10.18 6.96 6.96 7.30 10.68 7.30 7.30 RIVER_WAT 3.30 4.83 8.73 4.83 5.35 9.67 5.35 5.35 4.18 7.56 4.18 4.18 5.51 9.98 5.51 5.51

(b) Both Generators (Two TGs) and Grid are feeding power to the plant With Reactor Bus Information 3-Phase Fault Line-to-Ground Fault Line-to-Line Fault Line-to-Line-to-Grd* =================== ==================== =========================== =========================== =========================== ID kV I"k ip Ik I"k ip Ib Ik I"k ip Ib Ik I"k ip Ib Ik ------------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ -----LAGOON 0.41 23.53 56.15 23.53 27.54 65.70 27.54 27.54 20.38 48.62 20.38 20.38 26.36 62.90 26.36 26.36 NA 11.00 4.09 6.09 4.09 2.90 4.32 2.90 2.90 3.54 5.28 3.54 3.54 4.03 6.01 4.03 4.03 NA1 11.00 3.04 4.53 3.04 2.09 3.11 2.09 2.09 2.63 3.93 2.63 2.63 2.91 4.33 2.91 2.91 NJ 11.00 2.13 5.19 2.13 2.11 5.13 2.11 2.11 1.85 4.49 1.85 1.85 2.22 5.39 2.22 2.22 Reactor_NA 11.00 6.46 13.57 6.46 6.18 12.97 6.18 6.18 5.60 11.76 5.60 5.60 6.87 14.42 6.87 6.87 Reactor_NJ 11.00 2.16 5.89 2.16 2.16 5.89 2.16 2.16 1.87 5.10 1.87 1.87 2.16 5.90 2.16 2.16 RIVER_WAT 3.30 4.25 7.71 4.25 4.86 8.82 4.86 4.86 3.68 6.68 3.68 3.68 4.97 9.01 4.97 4.97

Without Reactor Bus Information 3-Phase Fault Line-to-Ground Fault Line-to-Line Fault Line-to-Line-to-Grd* =================== ==================== =========================== =========================== =========================== ID kV I"k ip Ik I"k ip Ib Ik I"k ip Ib Ik I"k ip Ib Ik ------------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ -----LAGOON 0.41 35.88 79.85 35.88 37.65 83.79 37.65 37.65 31.07 69.15 31.07 31.07 37.35 83.11 37.35 37.35 NA 11.00 4.78 6.93 4.78 3.14 4.55 3.14 3.14 4.14 6.00 4.14 4.14 4.56 6.60 4.56 4.56 NA1 11.00 3.42 4.99 3.42 2.23 3.25 2.23 2.23 2.97 4.32 2.97 2.97 3.20 4.65 3.20 3.20 NJ 11.00 9.63 16.76 9.63 8.32 14.49 8.32 8.32 8.34 14.52 8.34 8.34 10.11 17.61 10.11 10.11 RIVER_WAT 3.30 4.57 8.10 4.57 5.14 9.11 5.14 5.14 3.96 7.01 3.96 3.96 5.31 9.42 5.31 5.31

Power System Studies : HPCL-Nagaon Paper Mill

IV-13

Power System Studies : HPCL-Nagaon Paper Mill 4.7 Equipment Short Circuit Ratings The fault currents obtained at various locations are compared with short circuit rating of the network equipment and switchgear. Since the values of the short-circuit currents are on the lower side the equipment and switchgear can sustain the same. 4.8 Conclusions and Recommendations The short-circuit studies were carried out for the cases where both the Generators feeding power to the plant as well as only Grid feeding power to the plant. It is observed that the fault currents are of lower magnitudes. The short circuit calculation was also done for the system with current limiting reactor in the feeder NA and NN. The study shows that the fault current is reduced by the current limiting reactor, but the reduction in current is not very much significant. Hence there is no considerable benefit obtained by putting current limiting reactor in the feeders.

IV-14

Power System Studies : HPCL-Nagaon Paper Mill

Chapter - V

Relay Coordination Study 5.1

Introduction

Relay co-ordination means quality of selectivity among the protective devices, particularly in overcurrent devices. Over-current devices (and their variants) represent the largest installed base of protective equipment in any power system and may be considered the backbone of any protection strategy. Over-currents in a power distribution system can occur as a result of both normal (motor starting, transformer inrush, etc.) and abnormal (ground fault, line-to-line fault, etc.) conditions. In either case, the basic purposes of current-sensing protective devices are to detect the abnormal over-current with proper coordination, to operate selectively and to protect equipment properly while minimizing the outage of the remainder of the system. Primary and Back-up Protection Many factors may cause the protection failure and there is always some possibility of a circuit breaker failure. For this reason, it is usual to supplement primary protection with other systems to back-up the operation of the main system and to minimize the possibility of failure to clear a fault from the system. Primary Protection : The protective system which is normally expected to operate in response to a fault in the protected zone. Back- up Protection : A protective system intended to supplement the main protection in case the latter should be ineffective, or to deal with faults in those parts of the power system that are not readily included in the operating zones of the main protection. Back-up protection may be obtained automatically as an inherent feature of the main protection schemes, or separately by means of additional equipment. Time graded scheme such as over-current protection schemes is an example of providing inherent back-up protection. The extent and type of back-up protection, which is applied, will naturally be related to the failure risks and relative economic importance of the system. Protective Device Coordination Study A protective device coordination study is used to provide a basis for selecting and setting protective devices in order to isolate and clear faulty section as quickly and safely as possible, while all other protective devices remain closed, continuing power to the entire unfaulted part of the system. The study should be performed prior to the final approval of equipment submittals in order to select or to verify the selection of power fuse ratings, protective-relay characteristics and settings, ratios, and characteristics of associated voltage and current transformers, and low-voltage breaker trip characteristics and settings. To perform a coordination study, the following items will generally be required: a) b) c)

A one-line diagram of the power system involved, showing the type and rating of the protective devices and their associated current transformers. The impedance in ohms, percent or per unit of all power transformers, rotating machines and feeder circuits. The maximum and minimum values of short circuit currents that are expected to flow through each protective device.

V-1

Power System Studies : HPCL-Nagaon Paper Mill d)

The starting current requirements of motors and the starting and stalling times of induction motors. The maximum peak load current through protective devices. Decrement curves showing the rate of decay of the fault current supplied by the generators. Performance curves of the current transformers.

e) f) g)

The study should include all voltage classes of equipment from the utility's incoming line to down protective devices including each motor control center and panel board. The phase and ground overcurrent protection as well as settings for all other adjustable protective devices should be included. To assure complete coordination, the time-trip characteristics of all devices in series should be plotted on a single sheet of standard log-log paper. Devices of different-voltage systems can be plotted on the same sheet by converting their current scales, using the voltage ratios, to the same voltage basis. The selection and settings of the protective devices should be individually tabulated in a form, listing circuit identification, current transformer ratios, manufacturer, type, range of adjustment, and recommended settings. A tabulation of the recommended power fuse selection should be provided for all fuses in the system. 5.2

Different Criteria Considered for Relay Coordination

There are two basic adjustable settings on all inverse time relays; one is the time multiplier setting (TMS) and the other is the current setting usually known as the plug setting multiplier (PSM).

T Tm

TMS = Where, T

=

the required time of operation

Tm = the time obtained from the relay characteristics curve at TMS=1.0 and using the PSM equivalent to maximum fault current

PSM =

Pr imary current Pr imary current Pr imary current = = Pr imary setting current Re lay current setting × CT Ratio Pr imary operating current

Selection of current setting It is necessary to calculate the maximum fault current, which can occur at each relay position. A three-phase fault (LLL) gives the maximum fault current and phase to phase fault (LL) gives the minimum fault current. These are the two extreme values of fault current and the relay has to respond between these conditions. On a radial system the lowest setting must be at the farthest end; the settings being increased for the subsequent relays towards the sources. As per Indian standards the operating value should not exceed 130% of the setting. Selection for time setting For selective operation when there are number of relays connected in series, the relay farthest from the source should be set to operate in the minimum possible time. For succeeding relays towards the source a time delay step is given. For inverse time over-current relays the time setting should be done at the maximum fault current. If the relay has proper selectivity at the maximum fault current, it

V-2

Power System Studies : HPCL-Nagaon Paper Mill will automatically have a higher selectivity at the minimum fault current, as the curve is more inverse on lower current region. Earth fault can be provided with normal over-current relays, if the minimum earth fault current is sufficient in magnitude. The magnitude of earth fault current is usually low compare to the phase fault currents because the fault impedance is much higher for earth fault then for phase faults. Fortunately the grading of earth fault relays, unlike over-current phase relays, is normally limited to one system voltage due to general use of delta / star step down transformer, as the earth fault in one section does not draw ground current from other parts. In order to gain sensitive and selective relay operation, proper selection of pick up & time dial is essential. DMT Relays Primary operating current (P.O.C.) ƒ

must lie above maximum running load current and largest drive starting current by safety margin.

ƒ

must lie below the lowest through fault current

ƒ

maximum load current includes motor full load current. Hence it is subtracted.

ƒ

Relevant for generally used DOL starting

Formula used

I F > P.O.C. > ( I RL + I STM − I FLM ) Where, P.O.C. =

Desired Primary Operating current of relay

IRL

=

Maximum running load current

ISTM

=

Highest rating drive starting current

IFLM

=

Highest rating drive full load current

IF

=

Minimum fault current relay to sense

Desired Pick Up

Pick Up ≥

Pr imary Operating Current ( P.O.C.) C.T . Ratio

Desired Operating Time

t1

=

t + td

Where, t1

=

Desired operating time

Power System Studies : HPCL-Nagaon Paper Mill t

=

Downstream breaker / fuse operating time

td

=

Discrimination time

Time Dial Set Point: V-3 Time dial setting available in steps. Nearest time dial setting selected.

IDMT Relays Primary Operating Current:

P.O.C. = I RL + I STM − I FLM Where, P.O.C. =

Desired Primary Operating current of relay

IRL

=

Maximum running load current

ISTM

=

Highest rating drive starting current

IFLM

=

Highest rating drive full load current

Desired relay pick up - PS (Plug Setting): Ratio of Primary Operating Current of Relay to CT Ratio (C.T.R)

PS =

P.O.C. ( I RL + I STM − I FLM ) = C.T .R. C.T .R.

Select the next higher available steps.

Actual Pr imary Operating Current = Selected Pick Up × C.T .R. Plug Setting Multiplier - PSM

PSM =

Fault Current Actual P.O.C.

Desired Relay Operating Time t1:

t1

=

t + td

where, t

=

Downstream relay / fuse operating time

td

=

Discrimination time

Desired Time Dial set point TMS (Time Multiplier Setting):

Power System Studies : HPCL-Nagaon Paper Mill

Desired relay operating time t1 = Desired TMS setting Re lay operating time @ selected PSM and TMS = 1.0 Selected Time Dial setting: Nearest Higher Time Dial setting selected. V-4 5.3

Schemes used in Protection System

Over-current Earth fault protection can be provided with only one over-current relay connected in the residual circuit. A current will flow to the relay winding only when a fault involving earth occurs. a)

Three phase + One earth fault Relay Scheme: It includes three phase over-current relays for phase fault detection and one earth fault over-current relay for ground fault detection as shown in figure 5.3.a).

CTs

Phase Relay E/F

Figure 5.3 a) Three phase + one earth fault relay scheme b)

Two phase + one earth relay scheme: For economic consideration this scheme is used. It includes two phase over-current relays for phase fault detection and one earth fault overcurrent relay for ground fault detection as shown in figure 5.3.b).

CTs

Phase Relay E/F

Power System Studies : HPCL-Nagaon Paper Mill Figure 5.3 a) Two phase + one earth fault relay scheme

5.4

Relay Co-ordination for HPCL-NPM

5.4.1

Schemes and Relays present in HPCL-NPM

V-5

Schemes The over-current and earth fault protection is provided by two over-current and one earth fault relay (2+1 scheme) as shown in figure 5.4.1 (a) & (b). The scheme discussed in section 5.3.

CTs

Phase Over-current + Instantaneous Earth Fault Instantaneous Relay Fig. 5.4.1 (a) 2+1 Scheme of Over-current with Instantaneous & Earth Fault (CDAG51)

CTs

Phase Over-current

Earth Fault Over-current Relay Fig. 5.4.1 (b) 2+1 Scheme of Over-current & Earth Fault (CDG31)

Relays : The over-current and earth fault protection are provided using English Electric Relays, the specification of which are as follows;

Power System Studies : HPCL-Nagaon Paper Mill CDAG51 : CDAG is a triple pole relay and comprises two induction disc units for phase fault protection and an instantaneous attracted armature unit in the center for restricted earth fault protection. CDAG31 is type of CDAG relay having inverse time / over-current units and an instantaneous earth fault unit of type CAG14. Thus, CDAG51 is a type of CDAG31 relay having highest instantaneous unit on the two outer overcurrent elements. CDG31 : Triple pole version of the CDG11 with three over-current units or two over-current unit and one earth fault unit in the center. CDG11 has inverse V-6time over-current characteristics. CAG14 : Instantaneous high stability circulating current relay. CAG19 : Instantaneous over-current and earth fault unit with a high drop off/ pick up ratio, low transient overreach and high thermal rating. CDV : Voltage controlled inverse time over-current relay 5.4.2

Nomenclature ( for feeders upstream & downstream)

S. No.

Feeder

Description

1.

NB1

11 kV Bus, 630 A, 350 MVA, 18.34 kA

2.

NB11

415 V Bus, Paper Machine Drive-1

3.

NB12

415 V Bus, Paper Machine Drive-1

4.

NB13

415 V Bus, Paper Machine Drive-1

5.

NC1

11 kV Bus, 630 A, 350 MVA, 18.34 kA

6.

NC11

415 V Bus, LCC No.1

7.

NC12

3.3 kV Bus, Stock Preparation

8.

NC13

415 V Bus, Unit S/S –1

9.

ND1

11 kV Bus, 630 A, 350 MVA, 18.34 kA

10.

ND11

3.3 kV Bus, Paper Machine with size press

11.

ND12

415 V Bus, Unit S/S-2

12.

ND13

415 V Bus, Unit S/S-3

13.

NI

11 kV Bus, 630 A, 350 MVA, 18.34 kA

14.

NI1

3.3 kV Bus, Water supply & distribution (mill)

15.

NI2

415 V Bus, Unit S/S-16

16.

NG

11 kV Bus, 630 A, 300 MVA, 18.34 kA

17.

NG1

3.3 kV Bus, Soda recovery boiler house & power house (connected from NG bus)

18.

NG2

415 V Bus, Unit S/S-11

19.

NH

11 kV Bus, 630 A, 350 MVA, 18.34 kA

20.

NH1

415 V Bus, Unit S/S-15

21.

NH2

3.3 kV Bus, Soda recovery boiler house & power house (connected from NH bus)

Power System Studies : HPCL-Nagaon Paper Mill 22.

NH3

415 V Bus, Unit S/S-12

23.

NH4

415 V Bus, LCC No.4

24.

NC2

11 kV Bus, 630 A, 350 MVA, 18.34 kA

25.

NC21

415 V Bus, LCC NO.2

26.

NC22

415 V Bus, Unit S/S –4

27.

NC23

3.3 kV Bus, Stock preparation

28.

NB2

11 kV Bus, 630 A, 350 MVA, 18.34 kA

29.

NB21

415 V Bus, Paper Machine Drive

30.

NB22

415 V Bus, Paper MachineV-7 Drive

31.

NB23

415 V Bus, Paper Machine Drive

32.

NE

11 kV Bus, 630 A, 350 MVA, 18.34 kA

33.

NE1

415 V Bus, Unit S/S-7

34.

NE2

415 V Bus, Unit S/S-8

35.

NE3

415 V Bus, LCC No.3

36.

NE4

415 V Bus, CLO2 plant

37.

NL

11 kV Bus, 630 A, 350 MVA, 18.34 kA

38.

NL1

3.3 kV Bus, Chipper house

39.

NL2

415 V Bus, Unit S/S-13

40.

NL3

415 V Bus, LCC No.6

41.

NF

11 kV Bus, 630 A, 350 MVA, 18.34 kA

42.

NF1

3.3 kV Bus, Washing & screening and digester house

43.

NF2

415 V Bus, Unit S/S-9

44.

NF3

415 V Bus, Unit S/S-10

45.

ND2

11 kV Bus, 630 A, 350 MVA, 18.34 kA

46.

ND21

3.3 kV Bus, Paper machine-2 with size press

47.

ND22

415 V Bus, Unit S/S-5

48.

ND23

415 V Bus, Unit S/S-6

49.

NA

11 kV Bus near to TG connected to transmission line (6.2 km ‘Wolf’ )

50.

NA1

11 kV Bus near to transformer, at the end of transmission line (6.2 km ‘Wolf’ )

51.

DBB2

11 kV Bus connected to TG & ASEB supply

52.

NK

11 kV Bus, 1250 A, 350 MVA, 18.34 kA

53.

NK1

115 V Bus, 10 MVA Rectifier

54.

NK2

415 V Bus, Unit S/S-14

55.

NK3

415 V Bus, LCC No.5

56.

Lagoon

415 V Bus, Unit S/S-17

57.

Township

Power supply to colony

Power System Studies : HPCL-Nagaon Paper Mill 5.4.3

Co-ordination Criteria for Study

The following things have considered for the relay co-ordination study: (1)

It is assumed that 11 / 3.3 kV transformers have protection at secondary (CDG31) side at all the locations. Relay at the secondary side will act as a main protection for the fault at the secondary side. Over-current element of the relay (CDAG 51) at the primary side will act as a back up protection. Instantaneous element of relay (CDAG 51) at primary side is set such that it will not sense fault at the secondary side but will sense fault at the primary side. Thus, Instantaneous element of relay (CDAG 51) will serve as a main protection for the fault at the primary side.

(2)

Wherever there is no protection provided at secondary side then the relay at the primary side would have to act as a main protection for the fault at the secondary side. In such cases it is V-8 recommended to consider the relay settings without secondary side protection.

(3)

LG fault at the star side (secondary) of transformer is not reflected as LG fault to the delta side (primary) but is reflected as L-L fault on delta side. This point has been taken in to consideration.

(4)

At 3.3 kV feeder pick-up is set on the basis of the following criteria

Pr imary operating current = max imum running load current + highest drive starting current Highest drive starting current is taken as 6 times the full load current of the motor. (5)

Short circuit calculation has been done according to IEC-909.

(6)

Relays settings are such that, it will sense minimum fault current but at the same time, care is taken for the enough discrimination for the maximum fault current.

(7)

All the relay characteristics are 3 sec at PSM =10 except at NK, Lagoon & Township feeders.

5.4.4

Relay Co-ordination for Different Condition of Operation

Relay co-ordination is done for different possible condition of operation, which is given below. Case 1: Both generators ON In existing case, the settings of relay for DBB2-CB, Bus coupler C and DBB1-CB are same i.e., PS=0.75, TMS=0.8. For the fault at DBB1 bus, the fault current supplied by two generators is 13.47 kA. The current through Bus Coupler-C relay is 6.71 kA & through DBB1-CB relay is 13.47 kA. The time of operation of generator downstream relays of DBB1, Bus Coupler-C and DBB2 is 2 sec. & the time of open of generator relay is 1.86 sec. It results in tripping of generator relay first instead of downstream relays. In new settings, Bus Coupler CB relay and relay at DBB1-CB are set at same setting i.e., PS=0.75, TMS=0.3 & generator relays at PS=1.25, TMS=0.45. As the current through DBB1-CB is double than the Bus Coupler-C, the relay at Bus Coupler-C acts as a back-up protection operating at 1.027 sec. & the DBB-1 CB operating at 0.75 sec. will isolate the faulty section from the remaining. Thus generator continues feeding healthy Bus A, Bus B & DBB2 . Case 2: Generator B ON In case DBB1 bus is fed by generator B, the fault at DBB1 is supplied by generator B only. Same current of magnitude 0.671 kA will flow through DBB1-CB & generator CB. In existing settings

Power System Studies : HPCL-Nagaon Paper Mill (generator relay PS=1.5, TMS=0.6) & DBB1-CB (PS=0.75, TMS=0.8), the operation time of DBB1-CB is 2 sec. & the operation time of generator relay is 1.26 sec. It results in open of generator B relay before DBB1-CB relay. By applying new settings with generator CB relay at PS=1.25 & TMS=0.45 & DBB-1 CB becomes 0.75 sec. & that of generator B relay 1.26 sec. which is desired situation.

Case 3: Generator A ON If settings of relays at DBB-1 CB and Bus Coupler-C remain same as in previous two cases, there is chance of mal-operation of Bus Coupler-C before DBB1-CB. To avoid this situation one may go to higher setting (TMS=0.325) relay at Bus Coupler C relay at 1.109 sec. instead of 1.027 sec. The new settings give desired operation & discrimination for V-9 previous two cases. Case 4: Supply from Grid with both Generators OFF With the proposed settings considered in case 1 & DBB1 & DBB2 are supplied from grid. Fault at bus B results in fault current of 8.7 kA. The same current through DBB1-CB relay is 0.904 sec. is less compare to relay at cable (1.206 sec.). It results in de-coupling of bus & DBB1 bus, which is desired.

Co-ordination with Respect to Under Voltage Relay Settings of under-voltage relay provided at genarator (27) should be set with delay of 1 sec. so as to get proper co-ordination between under-voltage relay and downstream relays of generator.

Case 1: Both Generators ON

1200/1 GEN A - CB

PS = 1.25 TMS = 0.45

1.26 Sec

1200/1 GEN B - CB

PS = 1.25 TMS = 0.45

1.26 Sec 6.710 kA

6.710 kA

13.470 kA

DBB2

BUS A 1200/1 DBB2 - CB

1200/1

BUS B

DBB1 1200/1

Bus Coupler C 6.710 kA

PS = 0.75 TMS = 0.30 1.027 Sec

DBB1 - CB

PS = 0.75 TMS = 0.3 0.75 Sec

13.470 kA

Power System Studies : HPCL-Nagaon Paper Mill

Case -2: Generator – B ON

V-10 1200/1 GEN A - CB

1200/1

PS = 1.25 TMS = 0.45

PS = 1.25 TMS = 0.45

1.26 Sec 6.710 kA 6.710 kA 1200/1

BUS A

DBB2 1200/1

BUS B

DBB1 1200/1

Bus Coupler C DBB1 - CB

DBB2 - CB

PS = 0.75 TMS = 0.3

6.710 kA

1.024 Sec Case –3 : Generator – A ON

1200/1 GEN A - CB

PS = 1.25 TMS = 0.45

1.26 Sec

1200/1 GEN B - CB

6.710 kA 6.710 kA

DBB2

BUS A 1200/1 DBB2 - CB

1200/1

BUS B

DBB1 1200/1

Bus Coupler C 6.710 kA

PS = 0.75 TMS = 0.30 1.027 Sec

DBB1 - CB

PS = 0.75 TMS = 0.3 1.024 Sec

6.710 kA

Power System Studies : HPCL-Nagaon Paper Mill

Case –4 : Supply from Grid with both Generators OFF

Grid V-11

ASEB 50/1

4.35 kA 1200/1

PS = 0.75 TMS = 0.4

4.35 kA 1200/1

1.508 Sec

PS = 0.75 TMS = 0.4 1.508 Sec

BUS C PS = 0.75 TMS = 0.4 1.2064 Sec 1200/1

8.7 kA

1200/1

1200/1

1200/1

GEN A - CB

GEN B - CB

PS = 0.75 TMS = 0.4

1200/1

1.2064 Sec

DBB2

1200/1

DBB2 - CB

BUS A

1200/1

BUS B

Bus Coupler C

8.7 kA 1200/1

DBB1 - CB

8.7 kA

PS = 0.75 TMS = 0.3 0.904 Sec

DBB1

Power System Studies : HPCL-Nagaon Paper Mill

5.4.5

Summary of Relay Settings

Feeder wise Single Line Diagram:

V-12

The diagram for with connectivity and CT Ratios are shown for each feeder. Feeder wise Relay Operating Characteristics: The each feeder relay operating characteristics are given on log-log sheet. The settings of each relay with calculated operating time are also mentioned on the graph sheet.

Power System Studies : HPCL-Nagaon Paper Mill

Feeder : DBB2 to NK Bus G1

V-13

CDV

G2 CDV

1200/1

A+B CDG31

1200/1

Cable

DBB2

600/5

800/1

CDG31

250/5

CDG31

CDG31

Cable

Cable

Cable

Colony

Lagoon

NK 800/5

150/5

50/5

CDAG51

CDAG51

T1 10 MVA 11/0.135 kV

T4 1.6 MVA 11/0.415 kV

CDAG51

T6 0.250 MVA 11/0.415 kV

Power System Studies : HPCL-Nagaon Paper Mill

Feeder: NB1 V-14

G2

G1 CDV

CDV

1200/1

A+B CDG31

400/5

Cable

NB1

150/5

NB11

CDAG51150/5

150/5

CDAG51

Cable

Cable

T4 1.6 MVA 11/0.433 kV

T4 1.6 MVA 11/0.433 kV

NB12

NB13

Paper machine drive-1

CDAG51

Cable

T4 1.6 MVA 11/0.433 kV

Power System Studies : HPCL-Nagaon Paper Mill

Feeder : NC1 V-20

G2

G1 CDV

CDV

1200/1

A+B CDG31

600/5

Cable

NC1 50/5

250/5

CDAG51

Cable

T6 0.250 MVA 11/0.415 kV

150/5

CDAG51

Cable

T3 3 MVA 11/3.3 kV

NC11

NC12

LCC No. 1

Stock preparation

CDAG51

Cable

T4 1.6 MVA 11/0.415 kV

NC13 Unit s/s -1

Power System Studies : HPCL-Nagaon Paper Mill

Feeder : ND1 V-26

G2

G1 CDV

CDV

1200/1

A+B 600/5

CDG31 Cable

ND1 250/5

150/5

CDAG51

CDAG51

Cable

Cable

Cable

T3 3 MVA 11/3.3 kV

T4 1.6 MVA 11/0.415 kV

T4 1.6 MVA 11/0.415 kV

CDAG51

ND11

150/5

ND12

ND13

Power System Studies : HPCL-Nagaon Paper Mill

Feeder: NI V-32

G2

G1 CDV

CDV

1200/ A+B

400/5 CDG31 Cable

NI 250/5

150/5 CDAG51

CDAG51

Cable

Cable

T3 3 MVA 11/3.3 kV

NI1 Water supply &

T4 1.6 MVA 11/0.415 kV

NI2

Power System Studies : HPCL-Nagaon Paper Mill

Feeder : NG V-38

G2

G1 CDV

CDV

1200/1

A+B 600/5

CDG31

Cable

NG 250/5

150/5 CDAG51

Cable

T3 3 MVA 11/3.3 kV

CDAG51

Cable

T4 1.6 MVA 11/0.415 kV

Power System Studies : HPCL-Nagaon Paper Mill

Feeder : NH V-44

G2

G1 CDV

CDV

1200/ A+B 600/5

CDG31

Cable

NH

150/5

250/5 CDAG51

Cable

T4 1.6 MVA 11/0.415 kV

150/5 CDAG51

Cable

T2 5 MVA 11/3.3kV

50/5 CDAG51

Cable

T4 1.6 MVA 11/0.415 kV

CDAG51

Cable

T6 0.25 MVA 11/0.415 kV

Power System Studies : HPCL-Nagaon Paper Mill

Feeder : NC2 V-50

G2

G1 CDV

CDV

1200/1

A+B CDG31

600/5

Cable

NC2 50/5

150/5

CDAG51

NC21

250/5

CDAG51

CDAG51

Cable

Cable

Cable

T6 0.250 MVA 11/0.415 kV

T4 1.6 MVA 11/0.433 kV

T3 3 MVA 11/3.3 kV

NC22

NC23

Power System Studies : HPCL-Nagaon Paper Mill

Feeder: NB2 V-56

G2

G1 CDV

CDV

1200/1

A+B CDG31

400/1

Cable NB2 150/5

150/5

CDAG51

CDAG51

Cable

Cable

T4 1.6 MVA 11/0.415 kV

NB21

150/5

NB22

T4 1.6 MVA 11/0.415 kV

NB23

CDAG51

Cable

T4 1.6 MVA 11/0.135 kV

Power System Studies : HPCL-Nagaon Paper Mill

Feeder : NE V-62

G2

G1 CDV

CDV

1200/1

A+B 400/5

CDG31

Cable

NE 150/5

150/5

CDAG51

Cable

T4 1.6 MVA 11/0.415 kV

NE1

NE2

60/5

50/5

CDAG51

Cable

CDAG51

Cable

Cable

T4 1.6 MVA 11/0.415 kV

NE3

CDAG51

T6 0.250 MVA 11/0.415 kV

NE4

T5 0.8 MVA 11/0.110 kV

Power System Studies : HPCL-Nagaon Paper Mill

Feeder: NL V-68

G2

G1 CDV

CDV

1200/ A+B

400/1 CDG31 Cable

NL

150/5

400/5

CDAG51

CDAG51

Cable

Cable

T3 3 MVA 11/3.3 kV

NL1

50/5

NL2

T4 1.6 MVA 11/0.415 kV

NL3

Cable

T6 0.25 MVA 11/0.415 kV

Power System Studies : HPCL-Nagaon Paper Mill

Feeder : NF V-74

G2

G1 CDV

CDV

1200/1

A+B 400/1

CDG31

Cable

NF 250/5

150/5

CDAG51 Cable

T3 3 MVA 11/3.3 kV

150/5

CDAG51

CDAG51

Cable

Cable

T4 1.6 MVA 11/0.415 kV

T4 1.6 MVA 11/0.415 kV

Power System Studies : HPCL-Nagaon Paper Mill

Feeder : ND2 V-80

G2

G1 CDV

CDV

1200/1

A+B CDG31

600/1

Cable

ND2 250/5

150/5

150/5

CDAG51

CDAG51

Cable

Cable

T3 3 MVA 11/3.3 kV

T4 1.6 MVA 11/0.415 kV

CDAG51

Cable

T4 1.6 MVA 11/0.415 kv

Power System Studies : HPCL-Nagaon Paper Mill

Feeder: NA V-86

G2

G1 CDV

CDV

1200/1

A+B CDG31

400/1

Transmission Line

NA CDAG51

250/5

Cable

T3 3 MVA 11/3.3 kV

Power System Studies : HPCL-Nagaon Paper Mill

V-92

Power System Studies : HPCL-Nagaon Paper Mill

RELAY CO-ORDINATION SUMMARY REPORT (without secondary settings) RELAY AT GENERATORS Sr. No

1

2

Feeder

Gen1

Gen2

Relay

CT Ratio

Relay Type

O/C Range 51 / 51G

O/C Settings Existing PS TMS

O/C Settings New PS

TMS

Inst Range 50 / 50 G

Inst Setting Existing

Inst Setting New

Phase

1200/1

CDV 62

0.5-2.0

1.5

0.6

1.25

0.45

---

---

---

Phase

1200/1

CDV 62

0.5-2.0

1.5

0.6

1.25

0.45

---

---

---

Phase

1200/1

CDV 62

0.5-2.0

1.5

0.6

1.25

0.45

---

---

---

Ground - N side

150/1

CDG12

0.15 ,02

0.15

0.30

0.15

0.20

---

---

---

Phase

1200/1

CDV 62

0.5-2.0

1.5

0.6

1.25

0.45

---

---

---

Phase

1200/1

CDV 62

0.5-2.0

1.5

0.6

1.25

0.45

---

---

---

Phase

1200/1

CDV 62

0.5-2.0

1.5

0.6

1.25

0.45

---

---

---

Ground – N side

150/1

CDG12

0.15 ,02

0.15

0.30

0.15

0.20

---

---

---

Inst Range 50 / 50 G

Inst Setting Existing

Inst Setting New

Comments

11 kV BUS A + B ( POWER HOUSE ) Sr. No

1

2

3

Feeder

Relay

CT Ratio

Relay Type

O/C Range 51 / 51G

O/C Settings Existing PS TMS

O/C Settings New PS

TMS

Suuply to

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.25

---

---

---

DBB2

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.25

---

---

---

Ground

1200/1

CDG31

0.2-0.8

0.1

0.3

0.2

0.20

---

---

---

Bus

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.30

---

---

---

Coupler C

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.30

---

---

---

Ground

1200/1

CDG31

0.1–0.4

0.1

0.2

0.1

0.35

---

---

---

Supply to

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.25

---

---

---

DBB1

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.25

---

---

---

Ground

1200/1

CDG31

0.1-0.4

0.10

0.30

0.1

0.3

---

---

---

V-98

Comments

If range 0.1-0.4 then 0.1 – 0.3

Power System Studies : HPCL-Nagaon Paper Mill

11 kV BUS - C (132 kV SUB STATION) Sr. No

1

2

3

4

Feeder

Relay

CT Ratio

Relay Type

O/C Range 51 / 51G

O/C Settings Existing PS TMS

O/C Settings New

Inst Range 50 / 50 G

Inst Setting Existing

Inst Setting New

PS

TMS

0.8

0.75

0.4

---

---

---

Supply to

Phase

1200/1

CDG31

0.5-2.0

0.75

DBB1

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.4

---

---

---

Ground

1200/1

CDG31

0.1-0.4

0.10

0.50

0.2

0.4

---

---

---

Supply to

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.4

---

---

---

DBB2

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.4

---

---

---

Ground

1200/1

CDG31

0.2-0.8

0.10

0.30

0.2

0.3

---

---

---

Incomer

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.4

---

---

---

from

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.4

---

---

---

Tr-1

Ground

1200/1

CDG31

0.1-0.4

0.10

0.50

0.10

0.5

---

---

---

Incomer

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.4

---

---

---

from

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.4

---

---

---

Tr-2

Ground

1200/1

CDG31

0.1-0.4

0.10

0.50

0.10

0.5

---

---

---

Inst Range 50 / 50 G

Inst Setting Existing

Inst Setting New

Comments

11 kV DBB-1 (POWER HOUSE) Sr. No

1

Feeder

Relay

CT Ratio

Relay Type

O/C Range 51 / 51G

O/C Settings Existing PS TMS

O/C Settings New PS

TMS

0.8

0.75

0.4

---

---

---

ASEB

Phase

1200/1

CDG31

0.5-2.0

0.75

Incomer

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.4

---

---

---

Ground

1200/1

CDG31

0.2-0.8

0.10

0.30

0.2

0.4

---

---

---

V-99

Comments

Power System Studies : HPCL-Nagaon Paper Mill

11 kV DBB-1 , DBB-2, Bus A, Bus B Outgoing Feeders Sr. No

1

2

3

4

5

6

7

8

9

Feeder

NB1

NB11

NB12

NB13

NC1

NC11

NC12

NC13

ND1

Relay

CT Ratio

Relay Type

O/C Range 51 / 51G

O/C Settings Existing PS TMS

O/C Settings New PS

TMS

Inst Range 50 / 50 G

Inst Setting Existing

Inst Setting New

Phase

400/5

CDG31

2.5 – 10

2.5

0.5

2.5

0.225

---

---

---

Phase

400/5

CDG31

2.5 – 10

2.5

0.5

2.5

0.225

---

---

---

Ground

400/5

CDG31

0.5-2.0

0.5

0.25

0.50

0.20

---

---

---

Phase

150/5

CDAG51

2.5-10

3.75

0.2

3.75

0.20

20-80

60

60

Phase

150/5

CDAG51

2.5-10

5.0

1.0

3.75

0.20

20-80

60

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.2

3.75

0.20

20-80

60

60

Phase

150/5

CDAG51

2.5-10

5.0

0.2

3.75

0.20

20-80

60

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.2

3.75

0.20

20-80

60

60

Phase

150/5

CDAG51

2.5-10

3.75

0.2

3.75

0.20

20-80

60

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

600/5

CDG31

2.5-10

3.75

0.5

3.75

0.2

---

---

---

Phase

600/5

CDG31

2.5-10

3.75

0.5

3.75

0.2

---

---

---

Ground

600/5

CDG31

0.5-2.0

0.75

0.3

0.50

0.20

---

---

---

Phase

50/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

20

40

Phase

50/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

20

40

Ground

50/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

250/5

CDAG51

2.5-10

5

0.2

6.25

0.15

20-80

40

70

Phase

250/5

CDAG51

2.5-10

5

0.2

6.25

0.15

20-80

40

70

Ground

250/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.2

3.75

0.15

20-80

40

60

Phase

150/5

CDAG51

2.5-10

3.75

0.2

3.75

0.15

20-80

40

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

600/5

CDG31

2.5-10

2.5

0.5

5.0

0.2

---

---

---

Phase

600/5

CDG31

2.5-10

2.5

0.5

5.0

0.2

---

---

---

Ground

600/5

CDG31

0.5-2.0

0.75

0.25

0.50

0.20

---

---

---

V-100

Comments

Power System Studies : HPCL-Nagaon Paper Mill Sr. No

10

11

12

13

14

15

16

17

18

19

Feeder

ND11

ND12

ND13

NI

NI1

NI2

NG

NG1

NG2

NH

Relay

CT Ratio

Relay Type

O/C Range 51 / 51G

Existing

New

PS

TMS

PS

TMS

Inst Range 50 / 50 G

Existing

New

Phase

250/5

CDAG51

2.5-10

3.75

0.2

8.75

0.15

20-80

40

70

Phase

250/5

CDAG51

2.5-10

3.75

0.2

8.75

0.15

20-80

40

70

Ground

250/5

CDAG51

---

---

---

---

---

0.5-20

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.2

3.75

0.2

20-80

40

55

Phase

150/5

CDAG51

2.5-10

3.75

0.2

3.75

0.2

20-80

40

55

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.2

3.75

0.2

20-80

40

55

Phase

150/5

CDAG51

2.5-10

3.75

0.2

3.75

0.2

20-80

40

55

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

400/5

CDG31

2.5-10

2.5

0.6

3.75

0.225

---

---

---

Phase

400/5

CDG31

2.5-10

2.5

0.6

3.75

0.225

---

---

---

Ground

400/5

CDG31

0.5-2.0

0.5

0.3

0.50

0.20

---

---

---

Phase

250/5

CDAG51

2.5-10

3.75

0.3

5

0.15

20-80

40

65

Phase

250/5

CDAG51

2.5-10

3.75

0.3

5

0.15

20-80

40

65

Ground

250/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.3

3.75

0.15

20-80

40

60

Phase

150/5

CDAG51

2.5-10

3.75

0.3

3.75

0.15

20-80

40

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

600/5

CDG31

2.5-10

5.0

0.6

5.0

0.2

---

---

---

Phase

600/5

CDG31

2.5-10

5.0

0.6

5.0

0.2

---

---

---

Ground

600/5

CDG31

0.5-2.0

0.5

0.3

0.50

0.20

---

---

---

Phase

250/5

CDAG51

2.5-10

5.0

0.3

10.0

0.15

20-80

60

70

Phase

250/5

CDAG51

2.5-10

5.0

0.3

10.0

0.15

20-80

60

70

Ground

250/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.3

3.75

0.15

20-80

60

55

Phase

150/5

CDAG51

2.5-10

3.75

0.3

3.75

0.15

20-80

60

55

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

600/5

CDG31

2.5-10

5.0

0.6

6.25

0.20

---

---

---

Phase

600/5

CDG31

2.5-10

5.0

0.6

6.25

0.20

---

---

---

Ground

600/5

CDG31

0.5-2.0

0.5

0.3

0.50

0.20

---

---

---

V-101

Comments

Power System Studies : HPCL-Nagaon Paper Mill Sr. No

20

21

22

23

24

25

26

27

28

29

Feeder

NH1

NH2

NH3

NH4

NC2

NC21

NC22

NC23

NB2

NB21

Relay

CT Ratio

Relay Type

O/C Range 51 / 51G

Existing

New

PS

TMS

PS

TMS

Inst Range 50 / 50 G

Existing

New

Phase

150/5

CDAG51

2.5-10

2.5

0.3

3.75

0.2

20-80

60

60

Phase

150/5

CDAG51

2.5-10

2.5

0.3

3.75

0.2

20-80

60

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

250/5

CDAG51

2.5-10

6.25

0.3

10.0

0.15

20-80

60

70

Phase

250/5

CDAG51

2.5-10

6.25

0.3

10.0

0.15

20-80

60

70

Ground

250/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.3

3.75

0.2

20-80

20

60

Phase

150/5

CDAG51

2.5-10

3.75

0.3

3.75

0.2

20-80

20

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

50/5

CDAG51

2.5-10

2.5

0.2

2.5

0.2

20-80

60

40

Phase

50/5

CDAG51

2.5-10

2.5

0.2

2.5

0.2

20-80

60

40

Ground

50/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

600/5

CDG31

2.5-10

3.75

0.6

3.75

0.2

---

---

---

Phase

600/5

CDG31

2.5-10

3.75

0.6

3.75

0.2

---

---

---

Ground

600/5

CDG31

0.5-2.0

0.5

0.3

0.50

0.20

---

---

---

Phase

50/5

CDAG51

2.5-10

2.5

0.2

2.5

0.2

20-80

20

40

Phase

50/5

CDAG51

2.5-10

2.5

0.2

2.5

0.2

20-80

20

40

Ground

50/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

2.5

0.3

2.5

0.2

20-80

40

60

Phase

150/5

CDAG51

2.5-10

2.5

0.3

2.5

0.2

20-80

40

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

250/5

CDAG51

2.5-10

3.75

0.3

6.25

0.15

20-80

40

70

Phase

250/5

CDAG51

2.5-10

3.75

0.3

6.25

0.15

20-80

40

70

Ground

250/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

400/1

CDG31

0.5-2.0

0.5

0.6

0.75

0.15

---

---

---

Phase

400/1

CDG31

0.5-2.0

0.5

0.6

0.75

0.15

---

---

---

Ground

400/1

CDG31

0.1-0.4

0.1

0.2

0.1

0.15

---

---

---

Phase

150/5

CDAG51

2.5-10

3.75

0.15

3.75

0.1

20-80

60

60

Phase

150/5

CDAG51

2.5-10

3.75

0.15

3.75

0.1

20-80

60

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

V-102

Comments

Power System Studies : HPCL-Nagaon Paper Mill Sr. No

30

31

32

33

34

35

36

37

38

39

Feeder

NB22

NB23

NE

NE1

NE2

NE3

NE4

NL

NL1

NL2

Relay

CT Ratio

Relay Type

O/C Range 51 / 51G

Existing

New

PS

TMS

PS

TMS

Inst Range 50 / 50 G

Existing

New

Phase

150/5

CDAG51

2.5-10

3.75

0.15

3.75

0.1

20-80

60

60

Phase

150/5

CDAG51

2.5-10

3.75

0.15

3.75

0.1

20-80

60

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.15

3.75

0.1

20-80

60

60

Phase

150/5

CDAG51

2.5-10

3.75

0.15

3.75

0.1

20-80

60

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

400/5

CDG31

2.5-10

2.5

0.6

3.75

0.2

---

---

---

Phase

400/5

CDG31

2.5-10

2.5

0.6

3.75

0.2

---

---

---

Ground

400/5

CDG31

0.5-2.0

0.5

0.3

0.50

0.20

---

---

---

Phase

150/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

40

60

Phase

150/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

40

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

40

60

Phase

150/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

40

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

50/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

40

40

Phase

50/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

40

40

Ground

50/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

60/5

CDAG51

2.5-10

5.0

0.5

7.5

0.3

20-80

50

80

Phase

60/5

CDAG51

2.5-10

5.0

0.5

7.5

0.3

20-80

50

80

Ground

60/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

400/1

CDG31

0.5-2.0

0.5

0.6

1

0.15

---

---

---

Phase

400/1

CDG31

0.5-2.0

1.0

1.3

1

0.15

---

---

---

Ground

400/1

CDG31

0.1-0.4

0.1

0.3

0.1

0.15

---

---

---

Phase

400/5

CDAG51

2.5-10

2.5

0.15

3.75

0.1

20-80

40

40

Phase

400/5

CDAG51

2.5-10

2.5

0.15

3.75

0.1

20-80

40

40

Ground

400/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

2.5

0.125

2.5

0.125

20-80

40

60

Phase

150/5

CDAG51

2.5-10

2.5

0.125

2.5

0.125

20-80

40

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

V-103

Comments

Power System Studies : HPCL-Nagaon Paper Mill Sr.

Feeder

Relay

No

40

41

42

43

44

45

46

47

48

49

NL3

NF

NF1

NF2

NF3

ND2

ND21

ND22

ND23

NA

CT Ratio

Relay Type

O/C Range 51 / 51G

O/C Settings Existing PS TMS

O/C Settings New PS

TMS

Inst Range 50 / 50 G

Inst Setting Existing

Inst Setting New

Phase

50/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

20

40

Phase

50/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

20

40

Ground

50/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

400/1

CDG31

0.5-2.0

0.5

0.6

1.25

0.15

---

---

---

Phase

400/1

CDG31

0.5-2.0

0.5

0.6

1.25

0.15

---

---

---

Ground

400/1

CDG31

0.1-0.4

0.1

0.3

0.1

0.15

---

---

---

Phase

250/5

CDAG51

2.5-10

2.5

0.15

7.5

0.1

20-80

40

70

Phase

250/5

CDAG51

2.5-10

2.5

0.15

7.5

0.1

20-80

40

70

Ground

250/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.15

3.75

0.15

20-80

40

60

Phase

150/5

CDAG51

2.5-10

3.75

0.15

3.75

0.15

20-80

40

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.15

3.75

0.15

20-80

40

60

Phase

150/5

CDAG51

2.5-10

3.75

0.15

3.75

0.15

20-80

40

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

600/1

CDG31

0.5-2.0

0.75

0.6

1.0

0.125

---

---

---

Phase

600/1

CDG31

0.5-2.0

0.75

0.6

1.0

0.125

---

---

---

Ground

600/1

CDG31

0.1-0.4

0.1

0.3

0.1

0.15

---

---

---

Phase

250/5

CDAG51

2.5-10

3.75

0.15

8.75

0.1

20-80

40

70

Phase

250/5

CDAG51

2.5-10

3.75

0.15

8.75

0.1

20-80

40

70

Ground

250/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

40

55

Phase

150/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

40

55

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

40

55

Phase

150/5

CDAG51

2.5-10

2.5

2.5

0.15

20-80

40

55

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

400/1

CDG31

0.5-2.0

0.5

0.6

0.75

0.15

---

---

---

Phase

400/1

CDG31

0.5-2.0

0.5

0.6

0.75

0.15

---

---

---

Ground

400/1

CDG31

0.1-0.4

0.1

0.3

0.1

0.15

---

---

---

0.15

V-104

Comments

Power System Studies : HPCL-Nagaon Paper Mill Sr. No

50

Feeder

NA1

Relay

52

53

54

55

56

NK

NK1

NK2

NK3

LAGOON

TOWNSHIP

Relay Type

O/C Range 51 / 51G

O/C Settings Existing PS TMS

O/C Settings New PS

TMS

Inst Range 50 / 50 G

Inst Setting Existing

Inst Setting New

Phase

250/5

CDAG51

2.5-10

2.5

0.15

5.0

0.1

20-80

40

60

Phase

250/5

CDAG51

2.5-10

2.5

0.15

5.0

0.1

20-80

40

60

250/5

Ground

51

CT Ratio

Comments

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

800/1

CDG31

0.5-2.0

1.0

0.45

1.0

0.325

---

---

---

Phase

800/1

CDG31

0.5-2.0

1.0

0.45

1.0

0.325

---

---

---

1.3 Sec Characteristics

Ground

800/1

CDG31

0.1-0.4

0.1

0.3

0.1

0.25

---

---

---

1.3 Sec Characteristics

Phase

800/5

CDAG51

2.5-10

3.75

0.15

3.75

0.1

20-80

40

30

Phase

800/5

CDAG51

2.5-10

3.75

0.15

3.75

0.1

20-80

40

30

Ground

800/5

CDAG51

---

---

---

---

---

0.5-2.0

2.0

2.0

Phase

150/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

40

60

1.3 Sec Characteristics

Phase

150/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

40

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

50/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

20

40

Phase

50/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

20

40

Ground

50/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

600/5

CDG31

2.5-10

2.5

0.125

2.5

0.15

---

---

---

1.3 Sec Characteristics

Phase

600/5

CDG31

2.5-10

2.5

0.125

2.5

0.15

---

---

---

1.3 Sec Characteristics

Ground

600/5

CDG31

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

250/5

CDG31

2.5-10

2.5

0.125

2.5

0.15

---

---

---

1.3 Sec Characteristics

Phase

250/5

CDG31

2.5-10

2.5

0.125

2.5

0.15

---

---

---

1.3 Sec Characteristics

Ground

250/5

CDG31

---

---

---

---

---

0.5-2.0

0.5

0.5

V-105

Power System Studies : HPCL-Nagaon Paper Mill

RELAY CO-ORDINATION SUMMARY REPORT (with secondary settings) RELAY AT GENERATORS Sr. No

1

2

Feeder

Gen1

Gen2

Relay

CT Ratio

Relay Type

O/C Range 51 / 51G

O/C Settings Existing PS TMS

O/C Settings New PS

TMS

Inst Range 50 / 50 G

Inst Setting Existing

Inst Setting New

Phase

1200/1

CDV 62

0.5-2.0

1.5

0.6

1.25

0.45

---

---

---

Phase

1200/1

CDV 62

0.5-2.0

1.5

0.6

1.25

0.45

---

---

---

Phase

1200/1

CDV 62

0.5-2.0

1.5

0.6

1.25

0.45

---

---

---

Ground - N side

150/1

CDG12

0.15 ,02

0.15

0.30

0.15

0.20

---

---

---

Phase

1200/1

CDV 62

0.5-2.0

1.5

0.6

1.25

0.45

---

---

---

Phase

1200/1

CDV 62

0.5-2.0

1.5

0.6

1.25

0.45

---

---

---

Phase

1200/1

CDV 62

0.5-2.0

1.5

0.6

1.25

0.45

---

---

---

Ground – N side

150/1

CDG12

0.15 ,02

0.15

0.30

0.15

0.20

---

---

---

Inst Range 50 / 50 G

Inst Setting Existing

Inst Setting New

Comments

11 kV BUS A + B ( POWER HOUSE ) Sr. No

1

2

3

Feeder

Relay

CT Ratio

Relay Type

O/C Range 51 / 51G

O/C Settings Existing PS TMS

O/C Settings New PS

TMS

Supply to

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.25

---

---

---

DBB2

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.25

---

---

---

Ground

1200/1

CDG31

0.2-0.8

0.1

0.3

0.2

0.20

---

---

---

Bus

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.30

---

---

---

Coupler C

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.30

---

---

---

Ground

1200/1

CDG31

0.1–0.4

0.1

0.2

0.1

0.35

---

---

---

Supply to

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.3

---

---

---

DBB1

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.3

---

---

---

Ground

1200/1

CDG31

0.1-0.4

0.10

0.30

0.1

0.3

---

---

---

V-106

Comments

If range 0.1-0.4 then 0.1 – 0.3

Power System Studies : HPCL-Nagaon Paper Mill

11 kV BUS - C (132 kV SUB STATION) Sr. No

1

2

3

4

Feeder

Relay

CT Ratio

Relay Type

O/C Range 51 / 51G

O/C Settings Existing PS TMS

O/C Settings New

Inst Range 50 / 50 G

Inst Setting Existing

Inst Setting New

PS

TMS

0.8

0.75

0.4

---

---

---

Supply to

Phase

1200/1

CDG31

0.5-2.0

0.75

DBB1

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.4

---

---

---

Ground

1200/1

CDG31

0.1-0.4

0.10

0.50

0.2

0.4

---

---

---

Supply to

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.4

---

---

---

DBB2

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.4

---

---

---

Ground

1200/1

CDG31

0.2-0.8

0.10

0.30

0.2

0.3

---

---

---

Incomer

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.4

---

---

---

from

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.4

---

---

---

Tr-1

Ground

1200/1

CDG31

0.1-0.4

0.10

0.50

0.10

0.5

---

---

---

Incomer

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.4

---

---

---

from

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.4

---

---

---

Tr-2

Ground

1200/1

CDG31

0.1-0.4

0.10

0.50

0.10

0.5

---

---

---

CT Ratio

Relay Type

Inst Range 50 / 50 G

Inst Setting Existing

Inst Setting New

Comments

11 kV DBB-1 (POWER HOUSE) Sr. No

1

Feeder

Relay

O/C Range 51 / 51G

O/C Settings Existing PS TMS

O/C Settings New PS

TMS

0.8

0.75

0.4

---

---

---

ASEB

Phase

1200/1

CDG31

0.5-2.0

0.75

Incomer

Phase

1200/1

CDG31

0.5-2.0

0.75

0.8

0.75

0.4

---

---

---

Ground

1200/1

CDG31

0.2-0.8

0.10

0.30

0.2

0.4

---

---

---

V-107

Comments

Power System Studies : HPCL-Nagaon Paper Mill

11 kV DBB-1 , DBB-2, Bus A, Bus B Outgoing Feeders Sr. No

1

2

3

4

5

6

7

8

9

Feeder

NB1

NB11

NB12

NB13

NC1

NC11

NC12

NC13

ND1

Relay

CT Ratio

Relay Type

O/C Range 51 / 51G

O/C Settings Existing PS TMS

O/C Settings New PS

TMS

Inst Range 50 / 50 G

Inst Setting Existing

Inst Setting New

Phase

400/5

CDG31

2.5 - 10

2.5

0.5

2.5

0.225

---

---

---

Phase

400/5

CDG31

2.5 - 10

2.5

0.5

2.5

0.225

---

---

---

Ground

400/5

CDG31

0.5-2.0

0.5

0.25

0.50

0.20

---

---

---

Phase

150/5

CDAG51

2.5-10

3.75

0.2

3.75

0.20

20-80

60

60

Phase

150/5

CDAG51

2.5-10

5.0

1.0

3.75

0.20

20-80

60

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.2

3.75

0.20

20-80

60

60

Phase

150/5

CDAG51

2.5-10

5.0

0.2

3.75

0.20

20-80

60

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.2

3.75

0.20

20-80

60

60

Phase

150/5

CDAG51

2.5-10

3.75

0.2

3.75

0.20

20-80

60

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

600/5

CDG31

2.5-10

3.75

0.5

3.75

0.225

---

---

---

Phase

600/5

CDG31

2.5-10

3.75

0.5

3.75

0.225

---

---

---

Ground

600/5

CDG31

0.5-2.0

0.75

0.3

0.50

0..20

---

---

---

Phase

50/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

20

40

Phase

50/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

20

40

Ground

50/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

250/5

CDAG51

2.5-10

5

0.2

6.25

0.2

20-80

40

70

Phase

250/5

CDAG51

2.5-10

5

0.2

6.25

0.2

20-80

40

70

Ground

250/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.2

3.75

0.15

20-80

40

60

Phase

150/5

CDAG51

2.5-10

3.75

0.2

3.75

0.15

20-80

40

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

600/5

CDG31

2.5-10

2.5

0.5

5.0

0.225

---

---

---

Phase

600/5

CDG31

2.5-10

2.5

0.5

5.0

0.225

---

---

---

Ground

600/5

CDG31

0.5-2.0

0.75

0.25

0.50

0.20

---

---

---

V-108

Comments

Power System Studies : HPCL-Nagaon Paper Mill Sr. No

10

11

12

13

14

15

16

17

18

19

Feeder

ND11

ND12

ND13

NI

NI1

NI2

NG

NG1

NG2

NH

Relay

CT Ratio

Relay Type

O/C Range 51 / 51G

Existing

New

PS

TMS

PS

TMS

Inst Range 50 / 50 G

Existing

New

Phase

250/5

CDAG51

2.5-10

3.75

0.2

8.75

0.2

20-80

40

70

Phase

250/5

CDAG51

2.5-10

3.75

0.2

8.75

0.2

20-80

40

70

Ground

250/5

CDAG51

---

---

---

---

---

0.5-20

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.2

3.75

0.2

20-80

40

55

Phase

150/5

CDAG51

2.5-10

3.75

0.2

3.75

0.2

20-80

40

55

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.2

3.75

0.2

20-80

40

55

Phase

150/5

CDAG51

2.5-10

3.75

0.2

3.75

0.2

20-80

40

55

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

400/5

CDG31

2.5-10

2.5

0.6

3.75

0.25

---

---

---

Phase

400/5

CDG31

2.5-10

2.5

0.6

3.75

0.25

---

---

---

Ground

400/5

CDG31

0.5-2.0

0.5

0.3

0.50

0.20

---

---

---

Phase

250/5

CDAG51

2.5-10

3.75

0.3

5

0.2

20-80

40

65

Phase

250/5

CDAG51

2.5-10

3.75

0.3

5

0.2

20-80

40

65

Ground

250/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.3

3.75

0.15

20-80

40

60

Phase

150/5

CDAG51

2.5-10

3.75

0.3

3.75

0.15

20-80

40

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

600/5

CDG31

2.5-10

5.0

0.6

5.0

0.225

---

---

---

Phase

600/5

CDG31

2.5-10

5.0

0.6

5.0

0.225

---

---

---

Ground

600/5

CDG31

0.5-2.0

0.5

0.3

0.50

0.20

---

---

---

Phase

250/5

CDAG51

2.5-10

5.0

0.3

10.0

0.2

20-80

60

70

Phase

250/5

CDAG51

2.5-10

5.0

0.3

10.0

0.2

20-80

60

70

Ground

250/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.3

3.75

0.15

20-80

60

55

Phase

150/5

CDAG51

2.5-10

3.75

0.3

3.75

0.15

20-80

60

55

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

600/5

CDG31

2.5-10

5.0

0.6

6.25

0.20

---

---

---

Phase

600/5

CDG31

2.5-10

5.0

0.6

6.25

0.20

---

---

---

Ground

600/5

CDG31

0.5-2.0

0.5

0.3

0.50

0.20

---

---

---

V-109

Comments

Power System Studies : HPCL-Nagaon Paper Mill Sr. No

20

21

22

23

24

25

26

27

28

29

Feeder

NH1

NH2

NH3

NH4

NC2

NC21

NC22

NC23

NB2

NB21

Relay

CT Ratio

Relay Type

O/C Range 51 / 51G

Existing

New

PS

TMS

PS

TMS

Inst Range 50 / 50 G

Existing

New

Phase

150/5

CDAG51

2.5-10

2.5

0.3

3.75

0.2

20-80

60

60

Phase

150/5

CDAG51

2.5-10

2.5

0.3

3.75

0.2

20-80

60

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

250/5

CDAG51

2.5-10

6.25

0.3

10.0

0.2

20-80

60

70

Phase

250/5

CDAG51

2.5-10

6.25

0.3

10.0

0.2

20-80

60

70

Ground

250/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.3

3.75

0.2

20-80

20

60

Phase

150/5

CDAG51

2.5-10

3.75

0.3

3.75

0.2

20-80

20

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

50/5

CDAG51

2.5-10

2.5

0.2

2.5

0.2

20-80

60

40

Phase

50/5

CDAG51

2.5-10

2.5

0.2

2.5

0.2

20-80

60

40

Ground

50/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

600/5

CDG31

2.5-10

3.75

0.6

3.75

0.225

---

---

---

Phase

600/5

CDG31

2.5-10

3.75

0.6

3.75

0.225

---

---

---

Ground

600/5

CDG31

0.5-2.0

0.5

0.3

0.50

0.20

---

---

---

Phase

50/5

CDAG51

2.5-10

2.5

0.2

2.5

0.2

20-80

20

40

Phase

50/5

CDAG51

2.5-10

2.5

0.2

2.5

0.2

20-80

20

40

Ground

50/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

2.5

0.3

2.5

0.2

20-80

40

60

Phase

150/5

CDAG51

2.5-10

2.5

0.3

2.5

0.2

20-80

40

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

250/5

CDAG51

2.5-10

3.75

0.3

6.25

0.2

20-80

40

70

Phase

250/5

CDAG51

2.5-10

3.75

0.3

6.25

0.2

20-80

40

70

Ground

250/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

400/1

CDG31

0.5-2.0

0.5

0.6

0.75

0.20

---

---

---

Phase

400/1

CDG31

0.5-2.0

0.5

0.6

0.75

0.20

---

---

---

Ground

400/1

CDG31

0.1-0.4

0.1

0.2

0.1

0.15

---

---

---

Phase

150/5

CDAG51

2.5-10

3.75

0.15

3.75

0.225

20-80

60

60

Phase

150/5

CDAG51

2.5-10

3.75

0.15

3.75

0.225

20-80

60

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

V-110

Comments

Power System Studies : HPCL-Nagaon Paper Mill Sr. No

30

31

32

33

34

35

36

37

38

39

Feeder

NB22

NB23

NE

NE1

NE2

NE3

NE4

NL

NL1

NL2

Relay

CT Ratio

Relay Type

O/C Range 51 / 51G

Existing

New

PS

TMS

PS

TMS

Inst Range 50 / 50 G

Existing

New

Phase

150/5

CDAG51

2.5-10

3.75

0.15

3.75

0.225

20-80

60

60

Phase

150/5

CDAG51

2.5-10

3.75

0.15

3.75

0.225

20-80

60

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.15

3.75

0.225

20-80

60

60

Phase

150/5

CDAG51

2.5-10

3.75

0.15

3.75

0.225

20-80

60

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

400/5

CDG31

2.5-10

2.5

0.6

3.75

0.2

---

---

---

Phase

400/5

CDG31

2.5-10

2.5

0.6

3.75

0.2

---

---

---

Ground

400/5

CDG31

0.5-2.0

0.5

0.3

0.5

0.2

---

---

---

Phase

150/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

40

60

Phase

150/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

40

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

40

60

Phase

150/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

40

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

50/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

20

40

Phase

50/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

20

40

Ground

50/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

60/5

CDAG51

2.5-10

5.0

0.5

7.5

0.3

20-80

50

80

Phase

60/5

CDAG51

2.5-10

5.0

0.5

7.5

0.3

20-80

50

80

Ground

60/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

400/1

CDG31

0.5-2.0

0.5

0.6

1

0.20

---

---

---

Phase

400/1

CDG31

0.5-2.0

1.0

1.3

1

0.20

---

---

---

Ground

400/1

CDG31

0.1-0.4

0.1

0.3

0.1

0.15

---

---

---

Phase

400/5

CDAG51

2.5-10

2.5

0.15

3.75

0.175

20-80

40

40

Phase

400/5

CDAG51

2.5-10

2.5

0.15

3.75

0.175

20-80

40

40

Ground

400/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

2.5

0.125

2.5

0.125

20-80

40

60

Phase

150/5

CDAG51

2.5-10

2.5

0.125

2.5

0.125

20-80

40

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

V-111

Comments

Power System Studies : HPCL-Nagaon Paper Mill Sr. No

40

41

42

43

44

45

46

47

48

49

Feeder

NL3

NF

NF1

NF2

NF3

ND2

ND21

ND22

ND23

NA

Relay

CT Ratio

Relay Type

O/C Range 51 / 51G

O/C Settings Existing PS TMS

O/C Settings New PS

TMS

Inst Range 50 / 50 G

Inst Setting Existing

Inst Setting New

Phase

50/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

20

40

Phase

50/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

20

40

Ground

50/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

400/1

CDG31

0.5-2.0

0.5

0.6

1.25

0.20

---

---

---

Phase

400/1

CDG31

0.5-2.0

0.5

0.6

1.25

0.20

---

---

---

Ground

400/1

CDG31

0.1-0.4

0.1

0.3

0.1

0.15

---

---

---

Phase

250/5

CDAG51

2.5-10

2.5

0.15

7.5

0.175

20-80

40

70

Phase

250/5

CDAG51

2.5-10

2.5

0.15

7.5

0.175

20-80

40

70

Ground

250/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.15

3.75

0.15

20-80

40

60

Phase

150/5

CDAG51

2.5-10

3.75

0.15

3.75

0.15

20-80

40

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

3.75

0.15

3.75

0.15

20-80

40

60

Phase

150/5

CDAG51

2.5-10

3.75

0.15

3.75

0.15

20-80

40

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

600/1

CDG31

0.5-2.0

0.75

0.6

1

0.20

---

---

---

Phase

600/1

CDG31

0.5-2.0

0.75

0.6

1

0.20

---

---

---

Ground

600/1

CDG31

0.1-0.4

0.1

0.3

0.1

0.15

---

---

---

Phase

250/5

CDAG51

2.5-10

3.75

0.15

8.75

0.175

20-80

40

70

Phase

250/5

CDAG51

2.5-10

3.75

0.15

8.75

0.175

20-80

40

70

Ground

250/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

40

55

Phase

150/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

40

55

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

150/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

40

55

Phase

150/5

CDAG51

2.5-10

2.5

2.5

0.15

20-80

40

55

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

400/1

CDG31

0.5-2.0

0.5

0.6

0.75

0.2

---

---

---

Phase

400/1

CDG31

0.5-2.0

0.5

0.6

0.75

0.2

---

---

---

Ground

400/1

CDG31

0.1-0.4

0.1

0.3

0.1

0.15

---

---

---

0.15

V-112

Comments

Power System Studies : HPCL-Nagaon Paper Mill Sr. No

50

Feeder

NA1

Relay

52

53

54

55

56

NK

NK1

NK2

NK3

LAGOON

TOWNSHIP

Relay Type

O/C Range 51 / 51G

O/C Settings Existing PS TMS

O/C Settings New PS

TMS

Inst Range 50 / 50 G

Inst Setting Existing

Inst Setting New

Phase

250/5

CDAG51

2.5-10

2.5

0.15

5.0

0.175

20-80

40

60

Phase

250/5

CDAG51

2.5-10

2.5

0.15

5.0

0.175

20-80

40

60

250/5

Ground

51

CT Ratio

Comments

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

800/1

CDG31

0.5-2.0

1.0

0.45

1.0

0.325

---

---

---

Phase

800/1

CDG31

0.5-2.0

1.0

0.45

1.0

0.325

---

---

---

1.3 Sec Characteristics

Ground

800/1

CDG31

0.1-0.4

0.1

0.3

0.1

0.25

---

---

---

1.3 Sec Characteristics

Phase

800/5

CDAG51

2.5-10

3.75

0.15

3.75

0.1

20-80

40

30

Phase

800/5

CDAG51

2.5-10

3.75

0.15

3.75

0.1

20-80

40

30

Ground

800/5

CDAG51

---

---

---

---

---

0.5-2.0

2.0

2.0

Phase

150/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

40

60

1.3 Sec Characteristics

Phase

150/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

40

60

Ground

150/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

50/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

20

40

Phase

50/5

CDAG51

2.5-10

2.5

0.15

2.5

0.15

20-80

20

40

Ground

50/5

CDAG51

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

600/5

CDG31

2.5-10

2.5

0.125

2.5

0.15

---

---

---

1.3 Sec Characteristics

Phase

600/5

CDG31

2.5-10

2.5

0.125

2.5

0.15

---

---

---

1.3 Sec Characteristics

Ground

600/5

CDG31

---

---

---

---

---

0.5-2.0

0.5

0.5

Phase

250/5

CDG31

2.5-10

2.5

0.125

2.5

0.15

---

---

---

1.3 Sec Characteristics

Phase

250/5

CDG31

2.5-10

2.5

0.125

2.5

0.15

---

---

---

1.3 Sec Characteristics

Ground

250/5

CDG31

---

---

---

---

---

0.5-2.0

0.5

0.5

V-113

Power System Studies : HPCL-Nagaon Paper Mill

Relay setting – 3.3 kV Sr. No

1

2

3

4

5

6

7

8

9

Feeder

NB11_S

NB12_S

NB13_S

NC12_S

ND11_S

NI1_S

NG1_S

NH2_S

NC23_S

Relay

CT Ratio

Relay Type

O/C Range 51 / 51G

O/C Settings Existing PS TMS

O/C Settings New PS

TMS

Inst Range 50 / 50 G

Inst Setting Existing

Inst Setting New

Phase

3000/5

CDG31

2.5-10

5.0

0.2

3.75

0.10

---

---

---

Phase

3000/5

CDG31

2.5-10

5.0

0.2

3.75

0.10

---

---

---

Ground

3000/5

CDG31

Phase

3000/5

CDG31

2.5-10

5.0

0.2

3.75

0.10

---

---

---

Phase

3000/5

CDG31

2.5-10

5.0

0.2

3.75

0.10

---

---

---

Ground

3000/5

CDG31

Phase

3000/5

CDG31

2.5-10

5.0

0.2

3.75

0.10

---

---

---

Phase

3000/5

CDG31

2.5-10

5.0

0.2

3.75

0.10

---

---

---

2.5-10

5.0

0.1

5.0

0.10

---

---

---

Ground

3000/5

CDG31

Phase

1200/5

CDG31

Phase

1200/5

CDG31

2.5-10

5.0

0.1

5.0

0.10

---

---

---

Ground

1200/5

CDG31

0.5-2.0

0.5

0.3

0.5

0.3

---

---

---

Phase

1200/5

CDG31

2.5-10

6.25

0.1

6.25

0.10

---

---

---

Phase

1200/5

CDG31

2.5-10

6.25

0.1

6.25

0.10

---

---

---

Ground

1200/5

CDG31

0.5-2.0

0.5

0.2

0.5

0.2

---

---

---

Phase

1200/5

CDG31

2.5-10

5.0

0.1

3.75

0.10

---

---

---

Phase

1200/5

CDG31

2.5-10

5.0

0.1

3.75

0.10

---

---

---

Ground

1200/5

CDG31

0.5-2.0

0.5

0.2

0.5

0.2

---

---

---

Phase

1200/5

CDG31

2.5-10

5.0

0.1

7.5

0.10

---

---

---

Phase

1200/5

CDG31

2.5-10

5.0

0.1

7.5

0.10

---

---

---

Ground

1200/5

CDG31

0.5-2.0

0.5

0.2

0.5

0.2

---

---

---

Phase

1200/5

CDG31

2.5-10

5.0

0.1

7.5

0.10

---

---

---

Phase

1200/5

CDG31

2.5-10

5.0

0.1

7.5

0.10

---

---

---

Ground

1200/5

CDG31

0.5-2.0

0.5

0.2

0.5

0.2

---

---

---

Phase

1200/5

CDG31

2.5-10

3.75

0.1

5.0

0.10

---

---

---

Phase

1200/5

CDG31

2.5-10

3.75

0.1

5.0

0.10

---

---

---

Ground

1200/5

CDG31

0.5-2.0

0.5

0.2

0.5

0.2

---

---

---

V-114

Comments

Power System Studies : HPCL-Nagaon Paper Mill Sr. No

10

11

12

13

14

15

Feeder

NB21_S

NB22_S

NL1_S

NF1_S

ND21_S

NA1_S

Relay

CT Ratio

Relay Type

O/C Range 51 / 51G

O/C Settings Existing PS TMS

O/C Settings New PS

TMS

Inst Range 50 / 50 G

Inst Setting Existing

Inst Setting New

Phase

3000/5

CDG31

2.5-10

5.0

0.2

5.0

0.10

---

---

---

Phase

3000/5

CDG31

2.5-10

5.0

0.2

5.0

0.10

---

---

---

Ground

3000/5

CDG31

Phase

3000/5

CDG31

2.5-10

5.0

0.2

5.0

0.10

---

---

---

2.5-10

5.0

0.2

5.0

0.10

---

---

---

Phase

3000/5

CDG31

Ground

3000/5

CDG31

Phase

1200/5

CDG31

2.5-10

2.5

0.1

3.75

0.10

---

---

---

Phase

1200/5

CDG31

2.5-10

2.5

0.1

3.75

0.10

---

---

---

Ground

1200/5

CDG31

0.5-2.0

0.5

0.2

0.5

0.2

---

---

---

Phase

1200/5

CDG31

2.5-10

2.5

0.1

5.0

0.10

---

---

---

Phase

1200/5

CDG31

2.5-10

2.5

0.1

5.0

0.10

---

---

---

Ground

1200/5

CDG31

0.5-2.0

0.5

0.2

0.5

0.2

---

---

---

Phase

1200/5

CDG31

2.5-10

3.75

0.1

6.25

0.10

---

---

---

Phase

1200/5

CDG31

2.5-10

3.75

0.1

6.25

0.10

---

---

---

Ground

1200/5

CDG31

0.5-2.0

0.5

0.2

0.5

0.2

---

---

---

Phase

1200/5

CDG31

2.5-10

2.5

0.1

3.75

0.10

---

---

---

Phase

1200/5

CDG31

2.5-10

2.5

0.1

3.75

0.10

---

---

---

Ground

1200/5

CDG31

0.5-2.0

0.5

0.2

0.5

0.2

---

---

---

V-115

Comments

Power System Studies : HPCL-Nagaon Paper Mill

5.4.6

Sample Calculations for DBB2 Feeder:

Feeder: DBB2 to NK Bus Gen-A

Gen-B 1200/1

CDV 62

3 sec

A+B 1200/1

CDG31 3 Sec

3.52 kA Cable

DBB2 800/1 CDG 31

250/5

600/5

CDG 31 1.3Sec

3.41 kA

CDG 31 1.3sec

1.3sec

Cable

Cable Cable

Colony

Lagoon 3.30 kA

3.38 kA

NK 150/5 CDAG51

800/5 3Sec

CDAG51

3Sec

50/5 CDAG51 3Sec

3.35 kA T1 10 MVA 11/0.135 kv

Reflected 2.79 kA NK11

227.94 kA

NK12

T4 1.6 MVA 11/0.415kV

T6 0.250 MVA 11/0.415 kV

Reflected 1 38 kA

Reflected 0.29 kA

NK2

36.57 kA

V-116

NK3

7.86 kA

Power System Studies : HPCL-Nagaon Paper Mill Sample Calculation for DBB2 Feeder 1. Relay NK1 C.T.R = 800/5 Relay Type : GEC CDAG 51 (50 + 51) Over-current IDMT Unit (51) 3 Sec Characteristic Pick up=(0.5 -2) x In , Step = 0.25 In Time Dial = 0.1 –1.0, Step=0.5 but can be taken as 0.25 Instantaneous Unit (50) Pick up=(4-16) x In Over-current IDMT Unit(51) A) Fault Current = 2.790 kA Reflected current at primary for fault at transformer secondary (Obtained from the Three phase Fault Calculation) Maximum Running load current = 524.86 Amp •

Pick up PS = Max. Running load current/C.T.R.=524.86x5/800 = 3.25 A

Set PS at 3.75 A • • • • •

Actual Primary operating current(P.O.C) = PS* C.T.R=3.75 *800/5 = 600 A PSM = Fault Current / Actual P.O.C = 2790/600 = 4.65 Operating time | PSM=4.65, TMS=1.0 = 0.14/(PSM0.02 -1) =4.48 sec Desired operating time =0.3 sec TMS = 0.3/4.48 = 0.066

Set TMS at 0.1 Actual operating time | PSM=4.65, TMS=0.1 = 0.41 sec (For Fault at Transformer secondary) B) Fault Current = 3.35 kA (Fault at the primary of the Rectifier transformer) • PSM = Fault Current / Actual P.O.C = 3350/600 = 5.58 Actual operating time| PSM=5.58, TMS=0.1 = 0.38 sec (For Fault at Transformer primary) Instantaneous element settings (50) Fault Current = 2.790 kA Reflected current at primary for fault at transformer secondary Margin provided is 30 % Primary operating current (P.O.C)=1.3×2.790=3.627 kA Pick up =PS=3627In/800=4.53 In=4.53×5 = 22.65 A PS > 22.65 A so that it should not sense 2.790 kA. Set at 30 A 2. Relay NK2 C.T.R = 150/5

V-117

Power System Studies : HPCL-Nagaon Paper Mill Relay Type :

GEC CDAG 51 (50 + 51) Over-current IDMT Unit (51) 3 Sec Characteristic Pick up=(0.5 -2) x In , Step = 0.25 In Time Dial = 0.1 –1.0, Step=0.5 but can be taken as 0.25 Instantaneous Unit (50) Pick up=(4-16) x In Over-current IDMT Unit(51) A) Fault Current = 1.38 kA Reflected current at primary for fault at transformer secondary (Obtained from the Three phase Fault Calculation) Maximum Running load current < 87.97 Amp •

Pick up, PS = 87.97x5/150 = 2.9 A.

Set PS at 2.5 A • • •

Actual Primary operating current (P.O.C) = 2.5×150/5 = 75 A PSM = Fault Current / Actual P.O.C = 1380/75 = 18.4 Operating time | PSM=18.4, TMS=1.0 = 0.14/(PSM0.02 -1) =2.33 sec

Set TMS at 0.15 Actual operating time| PSM=18.4, TMS=0.15 = 0.36 sec(For Fault at Transformer secondary) B) Fault Current = 3.35 kA (Fault at the primary of the Rectifier transformer) • PSM = Fault Current / Actual P.O.C = 3350/75 > 20 • Actual operating time| PSM=20, TMS=0.15 =0.34sec (For Fault at Transformer primary) Instantaneous Element settings (50) Fault Current = 1.38 kA Reflected current at primary for fault at transformer secondary Margin provided is 30 % Primary operating current (P.O.C)=1.3×1.38=1.794 kA Pick up =PS=1794In/150=11.96 In=11.96×5 = 59.8 A PS > 59.8 A so that it should not sense 1.38 kA. Set at 60 A 3. Relay NK3 C.T.R = 50/5 Relay Type :

GEC CDAG 51 (50 + 51) Over-current IDMT Unit (51) 3 Sec Characteristic Pick up=(0.5 -2) x In , Step = 0.25 In Time Dial = 0.1 –1.0, Step=0.5 but can be taken as 0.25 Instantaneous Unit (50) Pick up=(4-16) x In

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Power System Studies : HPCL-Nagaon Paper Mill Over-current IDMT Unit(51) A) Fault Current = 0.29 kA Reflected current at primary for fault at transformer secondary (Obtained from the Three phase Fault Calculation) Maximum Running load current =13.12 Amp •

Pick up, PS = 13.12x5/50 = 1.3 A Set PS at 2.5 A • • •

Actual Primary operating current (P.O.C) = 2.5 *50/5 = 25 A PSM = Fault Current / Actual P.O.C = 290/25 = 11.6 Operating time | PSM=11.6, TMS=1.0 = 0.14/(PSM0.02 -1) =2.78 sec

Set TMS at 0.15 Actual operating time | PSM=11.6, TMS=0.15= 0.42 sec (For Fault at Transformer secondary) B) Fault Current = 3.35 kA (Fault at the primary of the Rectifier transformer) • PSM = Fault Current / Actual P.O.C = 3350/75 > 20 • Actual operating time| PSM=20, TMS=0.15 =0.34sec (For Fault at Transformer primary) Instantaneous Element settings(50) Fault Current = 0.29 kA Reflected current at primary for fault at transformer secondary Margin provided is 30 % Primary operating current (P.O.C)=1.3×0.29=0.377 kA Pick up =PS=377In/150=2.51 In=2.51×5 = 12.56 A PS > 12.56 A so that it should not sense 0.29 kA. Set at 40 A 4. Relay NK C.T.R = 800/1 Relay Type : GEC CDAG 51 (51) Over-current IDMT Unit (51) 1.3 Sec Characteristic Pick up=(0.5 -2) x In , Step = 0.25 In Time Dial = 0.1 –1.0, Step=0.5 but can be taken as 0.25 (A) Fault Current = 3.35 kA fault at Nk1 Bus (Obtained from the Three phase Fault Calculation) Maximum Running load current =621.96 Amp •

Pick up, PS = 621.96x1/800 = 0.77 A

Set PS at 1 A • •

Actual Primary operating current (P.O.C) = 1 *800/1 = 800 A PSM = Fault Current / Actual P.O.C = 3350/800 = 4.18

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Power System Studies : HPCL-Nagaon Paper Mill •

Operating time | PSM=4.18, TMS=1.0 =1.90 sec

•

Desied operating time (Coordination with Instantaneous element) Downstream relay operating time = 0.05 (Instantaneous Element) Desied operating time=0.05 + discrimination time = 0.05 + 0.4 =0.45 sec Desied operating time (Coordination with the Over-current element) Downstream relay operating time = 0.37 (Instantaneous Element) Desied operating time=0.37 + discrimination time = 0.37 + 0.25 =0.62 sec

•

•

TMS = 0.62/1.90=0.3263

Set TMS at 0.325 Actual operating time| PSM=4.18, TMS=0.325 = 0.59 Sec(For Fault at Transformer secondary) (B) Fault Current = 3.41 kA (Fault just after CT) • PSM = Fault Current / Actual P.O.C = 3410/800 =4.26 • Actual operating time| PSM=4.26, TMS=0.325 = 0.60 sec (For Fault at Transformer primary) (C) Fault Current = 8.290 kA (Maximum fault current - Fault just after CT) • PSM = Fault Current / Actual P.O.C = 8290/800 =10.36 • Actual operating time| PSM=4.26, TMS=0.325 = 0.42 sec (For Fault at Transformer primary) 5. Relay DBB2 C.T.R = 1200/1 Relay Type : GEC CDAG 51 (51) Over-current IDMT Unit (51) 3 Sec Characteristic Pick up=(0.5 -2) x In , Step = 0.25 In Time Dial = 0.1 –1.0, Step=0.5 but can be taken as 0.25 (A) Fault Current = 3.41 kA fault at DBB2 Bus (Obtained from the Three phase Fault Calculation) •

Pick up, PS = 0.75 A

Set PS at 0.75 A • • • •

•

Actual Primary operating current (P.O.C) = 0.75 *1200 = 900 A PSM = Fault Current / Actual P.O.C = 3410/900 = 3.788 Operating time | PSM=3.788, TMS=1.0 =5.185 sec Desied operating time Downstream relay operating time = 0.665 Desied operating time=0.63 + discrimination time = 0.63 + 0.25 =0.88 sec TMS = 0.88/5.185=0.169

Set TMS at 0.25 (so that enough discrimination time is available for LL Fault) Actual operating time = 1.27 sec (For Fault at Transformer secondary)

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Power System Studies : HPCL-Nagaon Paper Mill (B) Fault Current = 8.290 kA (Maximum fault current - Fault just after CT) • PSM = Fault Current / Actual P.O.C = 8290/900 =9.21 • Actual operating time| PSM=9.21, TMS=0.25 = 0.76 sec (For Fault at Transformer primary) 5. Relay A+B Generator Protection (CDV 62) C.T.R = 1200/1 Relay Type : GEC CDV 62 (51) Over-current IDMT Unit (51) 3 Sec Characteristic at PSM =4 Pick up=(0.5 -2) x In , Step = 0.25 In Time Dial = 0.1 –1.0, Step=0.5 but can be taken as 0.25 (A ) Fault Current = 13.470 kA fault at A + B Bus (Maximum Fault Current - Obtained from the Fault Calculation) •

Pick up, PS = 1.25 A

Set PS at 1.25 A • • • •

•

Actual Primary operating current (P.O.C) = 1.25 *1200/1 = 1500 A PSM = Fault Current / Actual P.O.C = (13470/2) /1500 = 4.49 ( Both Generator share equal fault current ) Operating time | PSM=4.49, TMS=1..0 =2.8 Desired operating time Downstream relay operating time = 0.76 Desired operating time=0.76 + discrimination time = 0.76 + 0.4 =1.04 sec TMS = 1.04/2.8=0.37

Set TMS at 0.40 Actual operating time| PSM=4.49, TMS=1.25 = 2.8 x 0.4 = 1.12 sec

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Power System Studies : HPCL-Nagaon Paper Mill 5.5

State-of-the-art Protective relays

It is observed that most of the existing relays are of Electromechanical type which are not fast enough and flexible for optimum relay coordination. It is therefore suggested that state of the art relays like numerical relays are installed in some critical feeders. The advantages of Numerical Relays over the Electromagnetic Relays are : 1.

Most optimum protection to vital primary equipment due to: (i) 3-phase O/C + E/F protection with high set for S/C protection. (ii) Choice of multiple characteristics to exactly meet our need. (iii) Stepless settings with digital display to make precise setting (iv) Supervision of auxiliary power supply and internal self supervision of relay’s hardware and software ensure availability of protection all the time (v) Built in Local Breaker back-up protection for stuck breaker protection. (vi) High accuracy of +/- 2%

2.

Several other programming features gives greater flexibility.

3.

Digital display of all phase and neutral currents gives a feel of connected load.

4.

Memory of previous 5 faults both transient and permanent gives important information. Which help in analyzing the fault and wear of primary equipment. This in turn help in preventive maintenance and result in longer life of primary equipment and fewer outages.

5.

Positive operation and speedier clearance of genuine fault will minimize damages.

6.

Monetary value of this improved protection, looking at cost of primary equipment, costly repairs and prolonged down time can be several hundred time of small price difference between numeric and electromechanical relays.

7.

Smaller size which allows compact switchgear cubicles and control and Relay panels, which in turn results into, space saving and economy.

8.

Very high accuracy of measurement.

9.

Extremely low burden of current and voltage circuits, which result into: (i) Smaller size and economical design of CTs & PTs (ii) Permit larger resistance in measured circuits, which in turn allow cabling of relatively thinner cross section. (iii) Overall cost saving (iv) No variation in relay characteristics for a very long period

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Power System Studies : HPCL-Nagaon Paper Mill 5.6

Conclusion and Recommendations

•

Relay co-ordination study was carried out for existing system and relay settings under various fault types and locations. The worst case was considered for suggesting the new setting of the relays which can prevent unwanted tripping in the system due to downstream faults.

•

Following shortcomings in the existing relay settings were found after performing the detail analysis and simulation of system: -

The generator over-current relay (CDV) is set at PS=1.5 and TMS=0.6, the P.O.C. is 1800 A. These settings are quite high and generator takes long time to clear the fault. For example, the time of operation is 2.28 sec for fault current magnitude of 8.290 kA ( for fault at NK Bus). During the fault, the generator bus voltage dips. As generator over-current relay takes long time to clear the fault, under-voltage relay (which is instantaneous) operates before the over-current relay leading to undesired tripping of the generator.

-

DBB2 feeder relay (incoming from the Bus A&B) is set at PS=0.75 and TMS=0.8 which is very high. At these settings, relay will not operate for the downstream faults. The time of operation is 2.49 sec for fault current magnitude of 8.290 kA (Fault at NK Bus) which is higher compared to the generator over-current relay. It results in operation of relay at generator before the relay at DBB2 Bus.

-

Similarly DBB1 feeder relay (incoming from the A+B Bus ) is set at PS=0.75 and TMS=0.8 which is also very high. At these settings, relay will not operate for the downstream faults. Here also it results in operation of relay at generator before the relay at DBB1 Bus.

-

Instantaneous element (51) of CDAG 51 relay at feeder NK12 and NK13 is set at 40 A and 20 A respectively. These settings are low enough to sense the fault current for the fault at the secondary of the transformer. This is observed at most of the feeders.

-

Earth fault relay (CDG12 – Inverse time (long time delay) characteristic) at the neutral of generator is generally provided as a back-up protection for the earth fault. However there is no earth fault relay provided at the generator terminal. In this case this relay has to operate as a main protection for the earth fault at generator terminal.

-

For NB1 Feeder fault at the secondary side of transformer, relay at the primary side operates before the relay at the secondary side.

•

Considering the worst case scenario of faults under various operating conditions, new setting of the existing Electro-mechanical Relays were worked out. Recommended settings for the over-current relays are listed in tables in section 5.4.5 (Summary of Relay settings) which can prevent undesired tripping as explained above. For the instantaneous under-voltage relay on Generator, it is recommended to use this relay with time delay on drop-off of 1 second. This can prevent undesired tripping of generators on under-voltage due to downstream feeder faults.

•

It is observed that most of the existing relays are of Electromechanical type which are not fast enough and flexible for optimum relay co-ordination. It is therefore suggested that state-of-the-art Numerical Relays are installed in the system. The advantages of Numerical Relays over the Electromagnetic Relays are numerous: faster operation, flexibility in optimum setting which can be done in dual mode through computer for various operating conditions of the system resulting in increased reliability of the protection system. The investment on numerical relays can very well be recovered from the reduced undesired trippings in the system which leads to loss of production, wastage of material under processing, additional energy drawn from ASEB grid at higher rates, TG start-up cost, etc.

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Chapter - VI

Transient Analysis 6.1 Introduction to Transient Analysis Power system stability may be broadly defined as that property of a power system that enables it to remain in a state of operating equilibrium under normal operating conditions and to regain an acceptable state of equilibrium after being subjected to a disturbance. Traditionally, the stability problem has been one of maintaining synchronous operation after the disturbance has been removed. This aspect of stability is influenced by the dynamics of generator rotor angles and power angle relationships. In the evaluation of stability the concern is the behaviour of power system subjected to a transient disturbance. This disturbance may be small or large. The small disturbances in the form of load changes (load injection and load rejection) take place continuously and the system adjusts itself to the changing conditions. A short circuit on a critical element followed by its isolation by protective relays will cause variations in power, machine rotor speeds and bus voltages. The voltage variations will actuate both generator and its voltage control circuits (exciter and AVR) and the speed variations will actuate prime mover governors. The changes in voltage and frequency will affect loads on the system in varying degrees depending on their individual characteristics. In addition, devices used to protect individual equipment may respond to variations in system and thus affect the system performance. 6.2 Generator Control System Modeling Response of generator Governor and Automatic Voltage Regulator (AVR) play an important role during transient disturbances in the system. They act as per the abnormality in frequency and voltage respectively to bring them back to the normal values unless the disturbance is large enough to go beyond the control of the governor and AVR. The models of governor and AVR/Exciter for transient study were selected after studying the functional block diagrams of the same. In the absence of actual model (normally should have been provided by the manufacturer), these models can fairly represent the controllers for the transient study. The typical models selected are as given below.

Fig. 6.2 (a): Governor model used for simulation Where Input (Rotor Fr) Source (Fnom) Constant (Reg) LEAD-LAG (Freq. Sign) Limit (Pmax) R2 (Turbine) Output (Torque)

: : : : : : :

Frequency sensed at main generator rotor Nominal or reference frequency Regulation constant of the governor Lead-Lag transfer function represents the governor time lag. Limits on turbine input power Turbine transfer function Turbine output torque

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Power System Studies : HPCL-Nagaon Paper Mill

Fig. 6.2 (b)- AVR and Exciter model used for simulation Where Source (Vref) : Input (busB_vol) : Per Unit (PU) : LAG (AVR) : I (EXE) : Output (EFD) :

Reference voltage to the exciter Terminal voltage sensed at generator bus To convert into per unit AVR time lag transfer function Exciter transfer function Generator field voltage

6.3 System Disturbances The transient study of a system can be carried out by simulating disturbances on equipment or element which represent the most critical element in the system. Also the disturbance which can be regarded as the most severe one from stability point of view. In HPCL-NPM the feeders to various sections of the plant of the radial and almost identical excepting from the load point of view. Hence a representative bus/feeder i.e. NK bus was identified for transient studies. The transient performance of generators was studied for various disturbances on the critical bus NK. These studies have been done using present and proposed Over-Current (O/C) settings in coordination with Under-Voltage(U/V), Over-Voltage(O/V) and Under-Frequency(U/F) relays of both the generators. 6.3.1 Short-Circuits Case 1: Short Circuit on NK bus A three phase short circuit was created at the NK bus, and the generator behaviour was studied for this case. It was found that the initial dip in generator terminal voltage was large enough to operate the generators U/V relays (which has no delay element), instead of O/C relay operating at the downstream feeders. This contributed to the frequent tripping of the generators, as observed at HPCL-NPM. The time variation of the Bus A voltage, TG2 current, Current in cable from TG (at DBB2) to NK (CAB_DBB2_NK) and TG2 frequency during short circuit (with existing relay settings) at bus NK are as shown in figure 6.3.1 (a).

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Power System Studies : HPCL-Nagaon Paper Mill

U [pu] - BUS A

I [A] - TG2

I1 [A] - CAB_DBB2_NK

fsyn [Hz] - TG2

Fig. 6.3.1(a): With existing relay settings for a fault at NK. The above problem can be eliminated by introducing appropriate time delay in generator U/V relay. Simulations with a minimum time delay of 0.5 sec shows that during the fault at NK bus, it gets cleared by operation of O/C relay in feeder from DBB2 to NK bus. The generators recover after fault clearance. Similar conditions were observed in case of faults on NN and NJ buses feeding to Township and Lagoon. The time variation of the Bus A voltage, TG2 current, Current in cable from TG (at DBB2) to NK (CAB_DBB2_NK) and TG2 frequency during short circuit (with proposed time delay in generators U/V relay) at bus NK are as shown below.

Time (s)

Power System Studies : HPCL-Nagaon Paper Mill Fig. 6.3.1(b): With proposed relay settings and delay of 0.5sec in generator U/V relay for a fault at NK. Case 2 : Short Circuit on bus TG at DBB1

VI-3

As TG bus at DBB1 is very nearer to TG bus at Power House, the time delay of 0.5 sec in TG U/V relay is not enough to allow O/C relay (for proposed settings) at feeder going to TG bus at DBB1 to trip. It requires a minimum delay time of 1 sec in TG U/V relay. The time variation of the Bus A voltage, TG2 current, Current in cable from BUS B at P/H to TG bus at DBB1 (CAB_B_DBB1) and TG2 frequency during short circuit at bus NK are shown below (with 1 sec time delay in TG U/V relay).

Fig. 6.3.1(c): With suggested O/C relay settings (1 sec delay in TG U/V relay) for fault at DBB1 6.3.2 Load Injection and Rejection The largest load (C&C plant @ 7 MW) was selected to study the effect of load injection/rejection. It was observed that generators could regain the steady state after these disturbances. The present settings of U/F relays are good enough to keep the system stable. The time variation of voltage, active power, current, and frequency of one of the generator (TG2) during load injection and load rejection at NK bus are shown in Fig.6.3.2(a) and 6.3.2(b) respectively.

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Fig. 6.3.2(a): Load injection at NK

Fig. 6.3.2(b) : Load rejection at NK 6.3.3 Loss of generation and load shedding In this case, loss of one of the TGs (TG1) when both the TGs are feeding to the total plant load demand of 30.5 MW (with grid isolated) is considered. The time variation of voltage, active power, current, and frequency of the healthy generator (TG2) are shown below.

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Fig.6.3.3 (a): Loss of TG1 at load demand of 30.5 MW It can be observed from the above plots that U/F relay provided with TG2 trips approximately after 5s with rate of frequency decay at 11Hz/s on loss of TG1. In order that TG2 operates in healthy condition, it is required to reject a load equivalent to loss of generation. The figure 6.3.3(b) shows the time variation of TG2 parameters for load shedding of 15 MW in 3 stages. Stage 1 : Switch-off all the operating load (@ 9.5MW) at NH and DBB1 feeder (total load) at a frequency of 46 Hz with a delay of 0.1 sec. Stage 2 : Switch-off all the operating load (@ 3.8MW) at NC2 feeder at a frequency of 45.5 Hz with a delay of 0.1 sec. Stage 3 : Switch-off all the operating load (@ 2MW) at NE at a frequency of 45 Hz with a delay of 0.1 sec. Note: The selection of rejected load depends on the criticality of the connected load. But the total load rejected should be approximately equal to loss of generation. The time variation of voltage, active power, current, and frequency of one of the generator (TG2) during load shedding when TG1 out are as shown in figure 6.3.3(b). 6.3.4 Loss of Grid supply Since the generators (TGs) do not operate in synchronism with the grid, any disturbance or fault on the grid side does not affect the generator operation. In this case, only the load which is connected to the grid supply will be affected and the same may be required to be shifted to the TGs.

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Power System Studies : HPCL-Nagaon Paper Mill

Fig.6.3.3 (b): Load shedding (around 15 MW) on TG2 when TG1 out. 6.4 Conclusion •

The transient study of the system was carried out by simulating disturbances on critical element in the system. The disturbances considered in the studies are : Short Circuit Faults on load as well as TG buses, Load Injection and Rejection, Loss of generation and load shedding and Loss of Grid supply. These studies have been done using present and proposed Over-current relay settings in co-ordination with Under-voltage, Over-voltage and Under-frequency relays of the generators.

•

From the Transient Stability Studies it was observed that during downstream faults, the generator bus voltage dips leading to instantaneous tripping of TG on under-voltage. This problem can be eliminated by providing 1 sec delay for TG Under-voltage (U/V) Relay allowing the downstream relay to operate and isolate the faulty section.

•

The present settings of Under-frequency Relays are suitable to keep the system stable during injection/rejection of large load(s) in the system.

•

In the event of sudden loss of generation when the plant is running in isolation from grid, Cascade Tripping of other TG can be avoided by resorting to automatic load shedding scheme.

•

Since the generators (TGs) do not operate in synchronism with the grid, any disturbance or fault on the grid side does not affect the generator operation. In this case, only the load which is connected to the grid supply will be affected and the same may be required to be shifted to the TGs.

Power System Studies : HPCL-Nagaon Paper Mill

Chapter - VII

Harmonic Studies 7.1 Introduction to Power System Harmonics The presence of voltage and current waveform distortion is generally expressed in terms of harmonics frequency. The use of non-linear loads connected to electric power system include power converters, arc discharge devices, saturated magnetic devices, and, to lesser degree, rotating machines, causes harmonics problem within and outside the power system. Static power converters of electric power are the largest non-linear load and are used in industry for a variety of purposes, such as adjustable speed drive and uninterruptible power supplies (UPS). These devices are useful because they can convert ac to dc, dc to dc, dc to ac and ac to ac. A major effect of harmonic voltages and currents in rotating machinery (induction and synchronous) is increased heating due to iron and copper losses at the harmonic frequencies. The harmonic components thus affect the machine efficiency, overheating of the machines and can also affect the torque developed. Another problem is the excessive amount of interference induced into telephone circuits due to mutual coupling between the electrical system and the communication system at these harmonic frequencies. More recent problems involve the performance of static and digital relays, computers, numerical controlled machines and other sophisticated electronic equipment which are very sensitive to power line pollution. These devices can respond incorrectly to normal inputs, give false signals, or possibly not respond at all. The corrective action is always an expensive and unpopular solution, and more thought and investment are devoted at the design stage on the basis that prevention is better than cure. All the available cures cannot eliminate the harmonics completely; it can only be limited to acceptable level. IEEE 519-1992 allows the Total Harmonic Distortions (THD) as per the voltage levels. For 69 kV and below, the allowable total voltage distortion is 5 %. The scope of harmonic studies intends to establish goals for the design of electrical systems that include both linear, non-linear loads and requirement of harmonic filters to make harmonic distortion within the limit. 7.2 Disadvantages of Power System Harmonics The degree of which harmonics can be tolerated is determined by the susceptibility of the load (or power source) to them. The least susceptible type of equipment is that in which the main function is in heating, as in an oven or furnace. In this case, the harmonic energy generally is utilized and hence is quite completely tolerable. The most susceptible type of equipment is that whose design or constitution assumes a (nearly) perfect sinusoidal fundamental input. This equipment is frequently in the categories of communication or data processing equipment. A type of load that normally falls between these two extremes of susceptibility is the motor load. Most motor loads are relatively tolerant of harmonics. 7.2.1 Effects on Motors and Generators A major effect of harmonic voltages and currents in rotating machinery (induction and synchronous) is increased heating due to iron and copper losses at the harmonic frequencies. The harmonic components thus affect the machine efficiency, and can also affect the torque developed. Harmonic currents in a motor can give rise to a higher audible noise emission as compared with sinusoidal excitation. The harmonics also produce a resultant flux distribution in the air gap, which can cause or enhance phenomena called cogging (refusal to start smoothly) or crawling (very high slip) in induction motors. The sum effect of the harmonics is a reduction in efficiency and life of the machinery.

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Power System Studies : HPCL-Nagaon Paper Mill

7.2.2 Effects on Transformers With the exception that harmonics applied to transformers may result in increased audible noise, the effects on these components usually are those arising from parasitic heating. The effect of harmonics on transformers is twofold: current harmonics cause an increase in copper losses and stray flux losses, and voltage harmonics cause an increase in iron losses. The overall effect is an increase in the transformer heating, as compared to purely sinusoidal operation. It should be noted that the transformer losses caused by both harmonic voltages and harmonic currents are frequency dependent. The losses increase with increasing frequency and, therefore, higher frequency harmonic components can be more important than lower frequency components in causing transformer heating. 7.2.3 Effects on Power Cable Cables involved in system resonance at harmonic frequencies may be subjected to voltage stress and corona, which can lead to dielectric (insulation) failure. Cables that are subjected to “ordinary” levels of harmonic current are prone to heating. The flow of non-sinusoidal current in a conductor will cause additional heating over and above what would be expected for the rms value of the waveform. This is due to two phenomena known as “skin effect” and “proximity effect” both of which vary as a function of frequency as well as conductor size and spacing. 7.2.4 Effects on Capacitors A major concern arising form the use of capacitors in a power system is the possibility of system resonance. This affect imposes voltages and currents that are considerably higher than would be the case without resonance. The reactance of a capacitor bank decreases with frequency, and the bank, therefore, acts as a sink for higher harmonics current. This effect increases the heating and dielectric stresses. Frequent switching of nonlinear magnetic components (e.g., iron core), such as transformers and reactors, can produce harmonic currents that will add to the loading of capacitors. The result of the increased heating and voltage stress brought about by harmonics is a shortened capacitor life. 7.2.5 Effects on Switchgear and Relaying As with other types of equipment, harmonic currents can increase heating and losses in switchgear, thereby reducing steady-state current carrying capability and shortening the life of some insulating components. Fuses suffer a derating because of the heat generated by harmonics during “normal” operation. Protective relays generally do not respond to any one identifiable parameter such as the rms value of a primary quantity or the fundamental frequency component of that quantity. As a related consideration, the performance of a relay to a range of single frequency inputs is not an indication of how that relay will respond to a distorted wave containing those frequencies, Superposition does not apply. Multi-input relays may be more unpredictable than single input relays in the presence of wave distortion. Relay response under distorted conditions may vary among relays having the same nominal fundamental frequency characteristics, not only among different relay manufacturers, but also among different vintages of relay from the same manufacturer. The following are the effects of harmonics on relay operation as follows: 1. Relays exhibit a tendency to operate slower and/or with higher pickup values, rather than operate faster and/or with lower pickup values. 2. Static under-frequency relays are susceptible to substantial changes in operating characteristics. 3. In most cases, the changes in operating characteristics are relatively small over the moderate range of distortion expected during normal operation.

VII-2

Power System Studies : HPCL-Nagaon Paper Mill 4. For different manufacturers, over-voltage and over-current relays exhibit different changes in operating characteristics. 5. Depending on harmonic content, operating torques of relays are sometimes reversed. 6. Balanced beam impedance relays show both overreach and underreach, depending on the distortion. 7. Harmonics sometimes impair the high-speed operation of differential relays. 7.3 Harmonic Measurements ABB did the harmonic measurement at HPCL-NPM. It was observed that main harmonic sources in their system were NB1 and NB2, which are feeding to DC drives. The harmonic levels at NB1 and NB2 transformers secondary (415V side) are around 40% THD in current and 8% THD in voltage ( 5th order dominant). These harmonics reflect to HT side and have a 2% voltage THD. The detailed measured harmonic data is given in chapter-II, section 2.7.2. 7.4 Harmonic Analysis Since the major harmonic sources are DC drives connected to transformers at NB1 and NB2 buses, the following harmonic analysis is followed by injecting the harmonic current at NB1 and NB2 bus transformers secondary. The values injected at these buses are taken from the measurements as given in chapter-II, section 2.7.2. 7.4.1 Without Filters The following harmonic spectra give the THD in voltage and current at NB12 (NB1 SEC-B) and NB1.

Fig. 7.4 (a): Current THD in transformer at NB12

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Power System Studies : HPCL-Nagaon Paper Mill

Fig. 7.4 (b): Voltage THD at bus NB12

Fig. 7.4 (c): Voltage THD at bus NB1

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Power System Studies : HPCL-Nagaon Paper Mill

Fig. 7.4 (d): Current THD in feeder NB1 It was observed that these harmonics produce the maximum THD of 6.88% in voltage at 415V side of NB22 bus (NB2 SEC-B). These harmonics also reflect on 11kV side and produce around 2.3% THD in voltage at NB1 and NB2. Though the standard (IEEE 519-1992) allows this distortion, it is suggested that filters should be installed, as capacitor banks with current limiting reactors of around 6% are anyway required due to very poor power factors at both buses NB1 and NB2. 7.4.2 Suppression of Harmonics From the above analysis single tuned filters were designed at buses NB1 and NB2 to suppress the 5th order harmonics. CALPOS Harmonic Analysis module was used to design the Filter bank based on the measured harmonic data. The parameters for the filter bank are given below. 7.4.2.1 Harmonic Filter Bank Filter Parameters Table 7.4.2.1 (a) : Layout data of the filter at NB1 & NB2 Reactive power of filter Resonance frequency

1500 kVAR 250 Hz

Q factor

10 p.u

Nominal Voltage

11 kV

Nominal Frequency

50 Hz

Main capacitance per phase Inductance per phase

37.882 uF 10.699 mH

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Power System Studies : HPCL-Nagaon Paper Mill

Resistor resistance per phase

1.681 Ohm

Fundamental harmonic current per phase

78.7 A

Harmonic current per phase

24.7 A

Total current per phase

82.5 A

Reactor: Fundamental harmonic current per phase Harmonic current per phase Total current per phase Reactor losses per phase Main capacitance: Fundamental voltage phase-phase

78.7 A 24.7 A 82.5 A 11.44 kW 11.456 kV

Harmonic voltage (arith.) phase-phase

0.899 kV

Harmonic voltage (geom.) phase-phase Total current per phase Total voltage Ucu phase-phase Total voltage Uci phase-phase Total voltage Ucq phase-phase

0.718 kV 82.5 kV 12.174 kV 9.235 kV 11.568 kV

7.4.2.2 Analysis with Filter Bank The following harmonic spectrums give the THD in voltage and current at NB12 (NB1 SEC-B) and NB1 with above designed filters at NB1 and NB2.

Fig. 7.4.2(a): Current THD in transformer at NB12

Power System Studies : HPCL-Nagaon Paper Mill

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Fig. 7.4.2(b)- Voltage THD at bus NB12

Fig. 7.4.2(c): Voltage THD at bus NB1

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Power System Studies : HPCL-Nagaon Paper Mill

Fig. 7.4.2(d)- Current THD in feeder NB1 7.5 Conclusion and Recommendations •

From the harmonic measurement carried out in the plant it was observed that main harmonic sources in the system are DC drives on buses NB1 and NB2. The harmonic levels at NB1 and NB2 transformers secondary (415V side) are around 40% THD in current and 7.5% THD in voltage (5th order dominant).

•

It was observed from the simulations that these harmonics produce the maximum THD of 6.88% in voltage on 415V side of NB22 bus (NB2 SEC-B). These harmonics also reflect on 11kV side and produce around 2.3% THD in voltage at NB1 and NB2. Though the standard (IEEE 5191992) allows this distortion, it is suggested to install Filter Banks, as capacitor banks with current limiting reactors of around 6% are anyway required due to very poor power factors (0.51 and 0.48 respectively) at both the buses NB1 and NB2.

•

The installation of filters will reduce the THD in voltage at buses NB1 and NB12 to 1.4% and 4.57% respectively. The filters will also improve the power factor at NB1 and NB2 to 0.98 lag (from 0.51) and 0.91 lag (from 0.48) respectively.

VII-8

Power System Studies : HPCL-Nagaon Paper Mill

Chapter - VIII

Condition Monitoring and Diagnostics 8.1 Introduction to Condition Monitoring and Diagnostics (CMD) Among the factors affecting the service life of equipment for transmitting and distributing electrical power are wear & tear and the aging process. A realistic assessment of the condition of equipment involves the measurement of parameters that are relevant to ageing, interpretation of the acquired data using reference values/databases and expert knowledge of the equipment. The objective is to obtain reliable information in order to make the correct choice from the alternatives of Maintenance, Retrofit, or New installation. Benefits of CMD to operators of power system are : a) Optimised availability of resources b) Enhanced service to consumers/plants c) Reduced overall operating costs. Necessity A diagnosis is advisable in the following situations, for example: • When technical condition of important or critical equipment is unclear. • When information is required on which to base a decision on the postponement of an investment. • When particular item of equipment has been increasingly subject to failures • In order to obtain initial reference values as a basis for subsequent maintenance work or to identify trends in the aging process • To access the remaining service life of aged substation equipment • To put together cost optimised spare parts packages for older equipment The Diagnostic process The diagnostic process can be broken down into five successive steps: • Consulting Studies • Definition of Diagnostic Package • On Site Condition Assessment • Interpretation • Diagnostic Report 8.2 Suggested CMD on Switchgear and Transformers Tests on the Power and Instrument transformer: A transformer consists of: 1. Paper insulation 2. Oil insulation 3. Other auxiliaries There are various diagnostic tests available for the transformer but performing all these is a time taking process. In order to assess the condition of the transformer, it is essential to know the condition of the above parts. Here each part is taken separately and the various tests available on those are given. A brief summary of the tests is given in the table 8.2.

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Power System Studies : HPCL-Nagaon Paper Mill

Table 8.2: Tests on Transformers Tests on paper 1. Furan content of oil 2. D.P. (Degree of Polymerisation) of paper 3. Recovery Voltage test 4. C and Tan delta measurement 5. Insulation Resistance and Polarisation Index.

Tests on oil 1. Dissolved gas analysis 2. B.D.V 3. Tan delta of oil 4. Moisture content measurement 5. Specific gravity 6. Acidity

Other tests 1. Tap changer test 2. Capacitance of bushing 3. Tan delta of bushing

Recovery voltage measurement This is to measure the ageing of oil-paper insulation of the transformer. This measurement is based on interfacial polarization mechanism of insulation. It gives plot of recovery voltage verses time which helps to detect abnormal ageing of insulation. C and Dissipation factor (Tan δ ) This is to detect the losses due to conduction and partial discharges. Degradation of cellulose and increase in moisture content can cause loss of insulation due to increase in leakage current and partial discharges. This leads to increase in temperature of insulation and subsequently reduction in life. This measurement will identify if there is increase in conduction losses or partial discharge. Dissolved gas analysis of oil This is to interpret the concentration of free and dissolved gases in transformer oil and diagnose the internal condition of the transformer. A transformer in service is subjected to two types of stresseselectrical and thermal stresses. The insulating materials within the transformer can breakdown as a result of these stresses to yield gases. The relative quantities of the above gases vary according to the energy available for decomposition of oil. The gases mainly consist of hydrogen, light hydrocarbons, and carbon oxides. The concentration of these gases indicate the presence of a fault and type of fault. The gases dissolved in transformer oil can be separated by gas chromatography. The analysis of the concentration of the various gases and also the rate of rise of the concentration of these gases can provide valuable information on the present condition of the oil filled equipment. Furan content of oil This is to identify degradation of cellulose. The electrically insulating cellulosic papers used in instrument and power transformers undergoes degradation due to thermal stress over a period of time. This can be quantified by measuring the furan content (2 furfuraldehyde ) dissolved in the oil. Measurement of Tan δ of oil This is to measure the power factor of the insulating oil subjected to an alternating voltage. Power factor is also accepted as a reliable criteria for quality this is because the power factor is a measure of the A.C and D.C losses occurring in the oil. Dielectric and thermal failure will not occur if these losses are sufficiently small. The measurement of P.F also gives the ageing characteristics of the oil. Karl Fischer test (Water Content)

VIII-2

Power System Studies : HPCL-Nagaon Paper Mill This test can be used to detect moisture in mineral oils, in oil impregnated paper and paper pressboards. Moisture mainly causes a reduction of the dielectric strength and the resistivity of oil, it also accelerates the deterioration of the metallic parts and reduces the strength of paper insulation. The test should be performed once in three years and if the moisture content exceeds the threshold value, reconditioning of oil has to be carried out. Neutralization value of insulating oil This is to determine the total acidity of used and unused mineral insulating oils. Acids in the oil attack the insulation and core of the transformer and also cause the formation of sludge. Measurement of neutralization value at regular intervals gives data about acid level in the oil and timely action (filtration or reclamation) helps in minimizing the extent of damage caused by the acids in oil. Diagnostic tests on the Circuit Breaker Breaker diagnosis can be divided into: a) Diagnosis of Arc Chamber b) Diagnosis of Drive (mechanical parts) c) Diagnosis of Auxiliaries

Diagnosis of arc chamber 1. Dynamic resistance measurement

Diagnosis of the drive 1. Mechanism travel timing measurement 2. Damping measurement

Diagnosis of auxiliaries 1. Heaters 2. coils 3. SF6 gas density 4. Charging system

Although diagnostic testing can be done, replacement/ retrofitting of breakers are usually due to a) Original design parameters being insufficient b) Increasing number of defects c) Maintenance costs However, condition monitoring enables the determination of optimal instant for a revision without dismantling the breaker. Dynamic resistance measurement (DRM) The main aim of the test is to determine the condition of the arcing contacts by diagnostic testing. The test is very simple and consists of passing direct current through the breaker and measuring the voltage drop and current while the breaker is operated. The results are sent on to the breaker analyser or a computer, which then calculates and plots resistance as a function of time. The movement of the contact is also recorded simultaneously. This is super imposed with resistance measurements and the curve of resistance versus motion is obtained. The variation of resistance gives an accurate idea of the condition of the arcing contacts. Advantages 1. On certain types of breakers DRM can be used to measure the shortening of contacts 2. It can be used to determine the length of the contact. 3. It can be used on breakers, which have parallel main contacts. 4. This method gives accurate results. Travel and timing measurements Measure the speed of operation and operating time of the breaker. The motion diagram can be used to analyse the following details1. Contact over travel

VIII-3

Power System Studies : HPCL-Nagaon Paper Mill 2. Contact opening/ Closing timings 3. Mechanism travel/ velocity 4. Damping The above data can be used to study the mechanical condition of the circuit breaker. Other checks include: • • • • •

Stored energy in spring Operating force General lockout Closing lockout Auto reclosing lockout

Diagnosis of Disconnector Most of the disconnector defects are caused by standstill problems. Ageing due to mechanical wearout can be neglected. Assuming adequate maintenance and periodic inspections, the life of the disconnector can be estimated at around 25 years. Abnormalities in the arrester can be detected by 1. Infra-red imaging of the disconnector 2. Measurement of contact resistance Infrared camera can be used to detect hotspots in any equipment of the substation. The disconnector contacts may get heated up due to an increase in the contact resistance caused by poor contact or melting of the contacts. Heating can cause melting of the contacts which subsequently causes the contacts join. This may lead to failure in opening of the disconnector. Any overheating can be measured in time by using Infra- red temperature measuring equipment. Contact resistance may also be checked after taking a shut down. Increase in contact resistance calls for visual inspection of the contacts. Other checks may include1. Checking the drives 2. Checking the interlocks 3. Checking the post insulator 8.3 System Monitoring Sequence Event Recorder and Disturbance Recorder Maximum availability is essential in the power generation and transmission sector. Faults in transmission lines, substations etc. can cause very serious damage. Therefore it is very important to have means to examine each fault in detail, in order to detect weak spots in the system. Indactic® 650 fault analysing system records the history of a fault and permits its reconstruction and analysis. When a fault occurs, the system stores the waveforms and other states of the equipment. The cause and location of the fault can quickly be determined and the behaviour of the associated control and protection equipment can be monitored. Concrete measures can then be deduced from the analysis of such faults, to prevent future failures. On the whole, the use of the fault recorder has powerful advantages, which contribute to improving the availability of the plant. • Causes of faults can be quickly detected • Fault sources can be deduced • The fault locating facility pinpoints the geographical location of the fault • Protective designs and switching strategies can be refined • Future faults can be prevented

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Power System Studies : HPCL-Nagaon Paper Mill

Functions for an In-Depth Fault Analysis

Functions of XPERT System

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Power System Studies : HPCL-Nagaon Paper Mill

XPERT The expert function carries out calculations for working out the short-circuit duration, as well as the line voltage and current signal vectors on the basis of fault algorithms. The results of such a calculation take the form of printed summaries and text files. The text files can be rapidly transmitted to any evaluation station in the system. • A typical recording contains the short circuit time, type of fault, distance to the fault, duration of the fault, short circuit impedance, phase and angle values for the time before and after the fault occurred, as well as after a return of normal conditions etc. • Fast fault summary thanks to fast transmission time (text file) • Application-specific analysis of digital signals using the formula editor, e.g. analysis of digital events taking chronological interdependence into consideration • Simple use of formula editor with BASIC-like syntax • Results of fault locating in table form make subsequent further processing in other Windows programs easier CALC CALC can be used to derive useful data for in-depth fault analysis by means of additional calculations and combining of recorded signals. For example, the analysis of harmonics provides a yardstick of the quality of a voltage. Or it permits the calculation of the effective short-circuit power which has led to a damage of switching elements, using the measured short circuit currents and voltages. The loop impedance as a function of time (resistance and phase angle) derived from the sequence of the voltage and current is another possibility for CALC. • Application-specific calculations using formula editor and algebraic syntax • Sums, differences, products and quotients, of input signals • Library containing complex functions for calculating RMS values, impedance and power vectors, angle differences, harmonic contents, mains frequency eviations and values, using general mathematical functions

Power System Studies : HPCL-Nagaon Paper Mill XPERT: Additional fault values can be analysed using self-produced formulae with the expert function. IndBase IndBase is a database for the management and statistical analysis of fault locating results and expert analyses. Each fault that occurs is managed as a data set, in which the most important values are stored. A typical recording contains the station number andVIII-6 name, event number and date, trigger type and criterion, line name, type of fault, distance to fault and fault duration. • File administration with editing function and storable configuration data • Many search, sort and display options • Data export as text file

CALC: Self-produced calculation and combination of additional values for in-depth fault analysis. 8.4 Suggested Maintenance Practice In changing macroeconomic situation, new considerations regarding cost efficiency of equipment maintenance have led to a predictive maintenance strategy Reliability Centered Maintenance (RCM). Besides allowing for the technical condition of the equipment concerned, its importance in the network context is also taken into account. These two data are combined and evaluated in order to define the optimum sequence of maintenance work. Equipment importance in network pertains to factors such as unavailability of power and costs associated with power failure in network. Investment prioritization decisions often require optimum maintenance strategies. Maintenance costs can be reduced upto 30% as compared to time based maintenance, using RCM. Alternative investments can be deferred using condition assessment of equipment and can result in savings from such deferment. ABB’s CALPOS-MAIN© software is specifically designed taking in view these entire requirements and suggesting optimal cost strategies for valued customers. 8.5 Recommendations In order to keep the system in healthy condition with reduced interruptions it is suggested to have an efficient monitoring system using Sequence Event Recorder and/or Disturbance Recorder. By this, faults and abnormal conditions leading to faults can be identified and corrective action can be taken to prevent the interruptions. In the equipment level diagnostics tests and condition monitoring can be

Power System Studies : HPCL-Nagaon Paper Mill done to plan for enhancing the performance of the equipment. Based on the same Reliability Centered Maintenance (RCM) can be adopted in the plant level.

Power System Studies : HPCL-Nagaon Paper Mill

Chapter - IX

Conclusions and Recommendations The operation of an industrial power system requires comprehensive analysis to evaluate current system performance and to minimise system interruptions and their effect on overall operation of the plant. This also ascertains the effectiveness of alternative plans for system expansion. System study and comprehensive analysis was carried out for Nagaon Paper Mill (of Hindustan Paper Corporation Ltd) Power Supply System using computer software. Various studies covered under the same are : Load Flow (including Reactive Power Compensation and Motor Starting), Transient Stability, Short-Circuit, Relay Co-ordination and Harmonic Analysis. The total power demand of Nagaon Paper Mill(NPM) is 30.5MW which is entirely met with captive power generation with two 15 MW,11kV TGs. The power system is also connected to Assam State Electricity Board (ASEB) grid via two 132/11 kV transformers of 7.5 MVA each. As a standard practice, the plant mostly runs on captive generation with ASEB grid isolated. Supply from the ASEB grid is taken during emergency and sometimes some of the feeders are fed from grid but in isolation from the TG fed sub-system. This is to avoid any disturbance on grid to affect the captive generators. Some of the important issues in the operation of the plant with respect to electrical distribution system are : Frequent unwanted tripping of TGs due to disturbances in downstream feeders, Harmonic distortion due to DC drives in the system, Low power factor at ASEB grid incomers attracting penalty charges and flash-over in 11kV panels resulting in outage in power supply. The power system study started with collection of electrical equipment/system data, various operating conditions of the power system and issues involved. Visit was made by ABB personnel to the plant for collection/validation of data as well as carrying out online measurements to ascertain the existing operating conditions of loads and harmonics in the system. The data thus obtained was mapped into the Power System Analysis Software (CALPOS) developed by ABB. Initially the as-is study was carried out to validate the data as well as the simulation approach. Subsequently various operating scenarios and faults were simulated in order to arrive at the recommendations for the improvements. Following are the important conclusions made : Load Flow Studies (including Reactive Power Compensation and Motor Starting) •

Load Flow study was carried out for various As-is operating conditions of TGs, Loads and Grid. For the typical operating scenario i.e. when the Grid is in isolation and the two TGs feeding entire load of the plant, following simulation results are obtained : -

•

The TGs (TG1 and TG2) are slightly overloaded to around 105% Most of the buses are within ± 5% of the nominal voltage. All the element loadings were found to be within their rated capacity. The overall power factor was observed to be less than 0.8 lag. The power factors at NB1 and NB2 buses feeding to DC drives are 0.51 lag and 0.48 lag respectively which are very poor.

For the case of one TG operating at rated conditions and grid(ASEB) supplying the rest of the power. the grid (ASEB) has to supply 16.4 MW at a power factor of 0.687 lag, This leads to paying penalty charges to ASEB on account of poor power factor. The 7.5 MVA transformer (two numbers) are also getting overloaded.

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Power System Studies : HPCL-Nagaon Paper Mill •

It is not possible to feed entire plant load of 30.5 MW from ASEB grid, since the two transformers are rated at 7.5 MVA each totalling to just 15 MVA capacity. It is possible to operate in this condition only if load is reduced to 36.66% of the total load demand (30.5 MW) which puts 100% loading on the grid transformers. To make the loading on grid transformers 75 %, the load demand should be reduces to 26.66 % of average load demand.

•

It was observed that the cables from ASEB bus (at DBB1) to bus C and bus C to ASEB bus (at DBB2) are now used only for charging the ASEB buses at DBB1 and DBB2 for emergency load transfer. Depending on operational convenience, these cables can be used to share load from power house to TG bus at DBB2, along with the existing cable between bus A to TG at DBB2. This can be obtained by closing the bus couplers at DBB1 and DBB2, and opening the ASEB incomers at Bus C. This parallel path reduces the total losses by 196kW, and it also improves the voltage level at DBB2.

•

Motor starting analysis was done for the largest rating motor (800kW) with typical characteristics, at various motor buses. In all the cases the voltage drop in the bus is within 20 % which is allowed by the standards. The study was also carried out for successive starting of two 800kW motors with a time interval of 2.5 sec. The maximum voltage drop at the motor terminal in this case is less than 20%, which is acceptable. A time interval of less than 2.5sec between these two motor startings causes a voltage drop of more than 20% which is not allowed.

•

Two major improvement options have been explored which results in reduced losses in the system i.e. Reactive Power Compensation and Feeder Power Flow Optimization. This leads to a reduction of losses by about 309 kW. -

In the Reactive Power Compensation Option, it is suggested to install 10.4 MVAR Shunt Capacitor Banks and 3 MVAR of Filter Bank at various locations in the system as given below : Bus

Compensation Type

Rating

NK

5 MVAR

NB1

Shunt Capacitor Bank Shunt Capacitor Bank Shunt Capacitor Bank Filter Bank

1.5 MVAR

NB2

Filter Bank

1.5 MVAR

C A

•

0.4 MVAR 5 MVAR

In the Feeder Power Flow Optimization Option, rerouting in terms of Parallel feeding of power from DBB1 to DBB2 bus is proposed.

The above improvements call for an investment of Rs. 35-40 lakhs approximately on the Reactive Power Compensation and Filter Banks as mentioned above. This can result in annual savings to the tune of 25.9 lakhs plus the saving in low power factor penalty of 52.8 lakhs (as paid by HPCL-NPM in the year 2000-2001). This makes the payback of investment in approximately 6 months. Thereafter the net saving for the plant will be around 78.7 lakhs per annum. Additionally, the harmonics at Buses NB1 and NB2 will be suppressed resulting in better quality of power and prevention of bad effect of harmonics.

Short-Circuit Studies

Power System Studies : HPCL-Nagaon Paper Mill •

The short-circuit studies were carried out for the cases where both the Generators feeding power to the plant as well as only Grid feeding power to the plant. It is observed that the fault currents are of lower magnitudes. • The short circuit calculation was also done for the system with current limiting reactor in the feeder NA and NN. The study shows that the fault current is reduced by the current limiting reactor, but the reduction in current is not very much significant. Hence there is no considerable benefit obtained by putting current limiting reactor in the feeders. IX-2 Relay Co-ordination •

Relay co-ordination study was carried out for existing system and relay settings under various fault types and locations. The worst case was considered for suggesting the new setting of the relays which can prevent unwanted tripping in the system due to downstream faults.

•

Following shortcomings in the existing relay settings were found after performing the detail analysis and simulation of system: -

The generator over-current relay (CDV) is set at PS=1.5 and TMS=0.6, the P.O.C. is 1800 A. These settings are quite high and generator takes long time to clear the fault. For example, the time of operation is 2.28 sec for fault current magnitude of 8.290 kA ( for fault at NK Bus). During the fault, the generator bus voltage dips. As generator over-current relay takes long time to clear the fault, under-voltage relay (which is instantaneous) operates before the overcurrent relay leading to undesired tripping of the generator.

-

DBB2 feeder relay (incoming from the Bus A&B) is set at PS=0.75 and TMS=0.8 which is very high. At these settings, relay will not operate for the downstream faults. The time of operation is 2.49 sec for fault current magnitude of 8.290 kA (Fault at NK Bus) which is higher compared to the generator over-current relay. It results in operation of relay at generator before the relay at DBB2 Bus.

-

Similarly DBB1 feeder relay (incoming from the A+B Bus ) is set at PS=0.75 and TMS=0.8 which is also very high. At these settings, relay will not operate for the downstream faults. Here also it results in operation of relay at generator before the relay at DBB1 Bus.

-

Instantaneous element (51) of CDAG 51 relay at feeder NK12 and NK13 is set at 40 A and 20 A respectively. These settings are low enough to sense the fault current for the fault at the secondary of the transformer. This is observed at most of the feeders.

-

Earth fault relay (CDG12 – Inverse time (long time delay) characteristic) at the neutral of generator is generally provided as a back-up protection for the earth fault. However there is no earth fault relay provided at the generator terminal. In this case this relay has to operate as a main protection for the earth fault at generator terminal.

-

For NB1 Feeder fault at the secondary side of transformer, relay at the primary side operates before the relay at the secondary side.

•

Considering the worst case scenario of faults under various operating conditions, new setting of the existing Electro-mechanical Relays were worked out. Recommended settings for the overcurrent relays are listed in tables in section 5.4.5 (Summary of Relay settings) which can prevent undesired tripping as explained above. For the instantaneous under-voltage relay on Generator, it is recommended to use this relay with time delay on drop-off of 1 second. This can prevent undesired tripping of generators on under-voltage due to downstream feeder faults.

•

It is observed that most of the existing relays are of Electromechanical type which are not fast enough and flexible for optimum relay co-ordination. It is therefore suggested that state-of-the-art

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Power System Studies : HPCL-Nagaon Paper Mill Numerical Relays are installed in the system. The advantages of Numerical Relays over the Electromagnetic Relays are numerous: faster operation, flexibility in optimum setting which can be done in dual mode through computer for various operating conditions of the system resulting in increased reliability of the protection system. The investment on numerical relays can very well be recovered from the reduced undesired trippings in the system which leads to loss of production, wastage of material under processing, additional energy drawn from ASEB grid at higher rates, TG start-up cost, etc. Transient Stability •

The transient study of the system was carried out by simulating disturbances on critical element in the system. The disturbances considered in the studies are : Short Circuit Faults on load as well as TG buses, Load Injection and Rejection, Loss of generation and load shedding and Loss of Grid supply. These studies have been done using present and proposed Over-current relay settings in co-ordination with Under-voltage, Over-voltage and Under-frequency relays of the generators.

•

From the Transient Stability Studies it was observed that during downstream faults, the generator bus voltage dips leading to instantaneous tripping of TG on under-voltage. This problem can be eliminated by providing 1 sec delay for TG Under-voltage (U/V) Relay allowing the downstream relay to operate and isolate the faulty section.

•

The present settings of Under-frequency Relays are suitable to keep the system stable during injection/rejection of large load(s) in the system.

•

In the event of sudden loss of generation when the plant is running in isolation from grid, Cascade Tripping of other TG can be avoided by resorting to automatic load shedding scheme.

•

Since the generators (TGs) do not operate in synchronism with the grid, any disturbance or fault on the grid side does not affect the generator operation. In this case, only the load which is connected to the grid supply will be affected and the same may be required to be shifted to the TGs.

Harmonic Analysis •

From the harmonic measurement carried out in the plant it was observed that main harmonic sources in the system are DC drives on buses NB1 and NB2. The harmonic levels at NB1 and NB2 transformers secondary (415V side) are around 40% THD in current and 7.5% THD in voltage (5th order dominant).

•

It was observed from the simulations that these harmonics produce the maximum THD of 6.88% in voltage on 415V side of NB22 bus (NB2 SEC-B). These harmonics also reflect on 11kV side and produce around 2.3% THD in voltage at NB1 and NB2. Though the standard (IEEE 5191992) allows this distortion, it is suggested to install Filter Banks, as capacitor banks with current limiting reactors of around 6% are anyway required due to very poor power factors (0.51 and 0.48 respectively) at both the buses NB1 and NB2.

•

The installation of filters will reduce the THD in voltage at buses NB1 and NB12 to 1.4% and 4.57% respectively. The filters will also improve the power factor at NB1 and NB2 to 0.98 lag (from 0.51) and 0.91 lag (from 0.48) respectively.

Condition Monitoring and Diagnostics

Power System Studies : HPCL-Nagaon Paper Mill •

In order to keep the system in healthy condition with minimum interruptions it is suggested to have an efficient monitoring system using Sequence Event Recorder and/or Disturbance Recorder. By this, faults and abnormal conditions leading to faults can be identified and corrective action can be taken to prevent the interruptions. In the equipment level, diagnostics tests and condition monitoring can be done to plan enhanced performance of the equipment. More recent maintenance approach based on risk assessment - Reliability Centered Maintenance (RCM) can be adopted in the plant.

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